Science Citation Index”- a New Dimension in Indexing

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Reprhsted from 6cleM% May 8, 1664, Vol. 144, No. 3619, pages 649-6S4 “Science Citation Index”- A New Dimension in Indexing

This unique approach underlies versatile bibliographic systems for communicating and evaluating information.

Eugene Garfield Over a quarter of a century ago lative (6) and executive (7) branches H. G. Wells made a magnificent, if of government will add momentum to premature, plea for the establishment the inevitable trend toward establish- of a world information center, “the ment of a world information center. World Brain” (1). To Wells, the World The main purpose of this article is Brain became the symbol of interna- to provide some perspective on the tional intellectual cooperation in a science-information, or sciencc-’’indcx- world at peace. The realization, with- ing, ” problem: to review briefly the in our lifetime, of the physical and developments in citation indexing that intellectual achievement envisioned in have occurred over the past 10 years; Wor/d Brain no longer lies in the realm and to indicate why the recently pub- of science fiction. The ultimate spec- lished Science Cifation Index (8) is a ification for a World Brain must await harbinger of things to come—a fore- more fundamental studies and under- runner of the World Brain. standing of information science. HOW- The average scientist thinks a World ever, the increasing convergence of Brain would be extremely useful, The such previously unrelated fields as ge- possibility of having all recorded netics, linguistics, psychology, and knowledge at one’s fingertips is fasci- chemistry foretells exciting realign- nating. The librarian, however, emi- ments in classical conceptions of the nently more practical on this topic than “information” problem. Unquestion- the scientist, because he has learned ably there are many different forms to live with bibliographical poverty in and arrangements which a Worlcf Brain the midst of scientific wealth, thinks of could assume. Vannevar Bush’~ “Mem- the enormously detailed problems of ex” was a microfilm version of the bibliographic control (9). Therefore, universal fingertip library (2): Memex the librarian may be the one who best stimulated considerable speculation but appreciates the implications of the Sci- also produced some realistic work (3). em-e Ci/a/iorr Index for bibliographic Tukey’s “Information Ledger” is a re- control. It is the first really serious cent specification of the desiderata for attempt at universal bibliographical a universal information system (4). control of science literature since the More recently, Senders has given an turn of the century (10), On the other approximate quantitative measure of hand, tbe librarian is sometimes too the information content of the world’s acutely aware of the detailed problems libraries (5). Surely the increasing involved in compiling an international awareness of the science-information inventory of science—precisely what problem on the part of both the legis- the Science Citation Index is. I believe the need for such an inventory, for such bibliographic control, is indisput- The author is director of the Institute for ScL able (11). eirtific Information. Philadelphia. and lecturer in information retrieval at -the” University ‘of Whether or not citation indexes are Psmssylvania. useful is a question that has now been 525 , answered. We have enough favorable indexing will be a vital part of such experience in using them to know they total communication. are desirable and useful. However. a citation index must meet the same eco- nomic test that all products in our An Example society must meet: Does the cost justify the benefits? To measure its value to In June 1955 a paper appeared in the scientific community is not simple. Science entitled “Citation indexes for Do the cost and difficulties of retrieving science” (14): it was in part based on pertinent literature justify bypassing suggestions made by Adair (/5) and the literature and chancing a replica- Hart (/6). In 1957 there followed a tion of research? Or, as Maddox re- paper on the applicability of the ci- cently phrased the problem: “Is the tator system to patents (1 7), which literature worth keeping?” (12). The cited Hart (16) and Seidel (/8) in Weinberg Committee (7) maintains support of arguments for establishing a

that the literature is an integral part citation index to patents. In two SU”)- of the research process. Printed tom- sequent papers (19, 20) the a priori munication still has a long life expect- nature of conventional indexes was dis- ancy as a means of imparting current cussed in contrast to the a posteriori information and retrieving data; it will character of citation indexing. The re- be with us at least until we have de- lationship of the citation index to the veloped science communication to the problem of achieving a Unified Science point where all indexes, journals, Index was explored at the International books, and other printed media be- Conference on Scientific Information in come obsolete and a World Brain takes 1958 (21). Fano (22), Ernst (23), over. Meanwhile, the initial biblio- Tukey (24), Savage (25), Lipetz (26), graphic control necessary for establish- Kessler (27, 28), Atherton (29), and ing a World Brain is economically justi- Salton (30) have also pursued various fied by the immediate and interim ramifications and possibilities of cita- requirements of tbe expanding com- tion indexing. plex of science and technology. The foregoing bibliographic recapit- If we ever achieve “total communi- ulation is intended to emphasize, to the cation, ” a state of research nirvana, reader unfamiliar with citation indexes, then an enormous time-shared, random- both the advantages and the simplicity access computer memory will augment of citation indexing. The 17 papers man’s finite memory and replace print- cited in the preceding paragraph are ed indexes and catalogs. In this condi- associated here in this article. A citation of nirvanu a World Brain will it- tion index would automatically lead tbe self have become an auxiliary to user to this group of related works, man’s own brain, Or, as Bernal has provided he knew of any one of the stated it (/3), “The speculations of the cited references. With a citation index, future may then be the speculations, this article and the paragraph in ques- not of one man or of many men, but tion would be retrieved regardless of of all humtinity and their machines.” the date or the journals in which the But this achieven]ent will require a far cited papers originally appeared. The greater commitment to the task of scatter of the 17 references, however, accumulating and communicating sci- also illustrates some of the complexi- entific information than we have ever ties of compiling citation indexes. The been willing to make previously. In preceding paragraph is a historical- any event, the direct linking of con- bibliographic introduction comparable ceptual information which is made “pos- to that provided by many authors in sible for the first time through citation writing scientific papers.

526 Consider the reader who has never lative difference in no way alters the heard the term cilahn index but wants basic commonality of the two systems. information on this topic. His diffi- The information processed in the two culties in finding the article you are is exactly the same-citations appear- now reading will illustrate the difficul- ing in bibliographies. ties of finding information by conven- To continue our example—the litera- tional methods. It would be almost ture searcher interested in finding pub- impossible for one unfamiliar with the lished articles on “the citation index” citation-index concept to search for pa- by conventional methods faces a basi- pers under the heading “citation in. cally difficult task. Even though he dexing” because the term probably may have the terminology correct, or would not occur to him. If the idea nearly correct, he will find that Science of citation indexing did occur to him, is one of those journals that is .se/ec- the descriptive terminology that he se- fively indexed by the leading discipline- lected in searching for the citation- oriented indexing services, “Chemical” index “idea” would probably have been articles are indexed by Chemical A b- different. And yet, previous knowledge stracls, “physical” articles by Science of any one of the references cited in A bsfracts, “biological” articles by f?i- this article, or cited in any of the other ological A bstracts, and so on. But even 17 “citation-index papers,” would, if one assumes that the conventional through the use. of citation indexes, indexing services do abstract articles bring to the attention of the requester such as this, an additional degree of this “new” concept. Even in this cir- uncertainty is then introduced by the cuitous example there is no paradox possibility (and too often the prob- involved in calling the results of the ability) that either the indexer or the search a “new” concept, since the searcher did not use the “correct” actual search could have been per- terminology. Concepts or ideas are ex- formed by some other person using a tremely difficult to handle consistently citation index, while the requester him- in classical subject indexes. self remained unaware of its existence. For the other papers in the list of Thus, interest in Vannevar Bush’s pa- 17 citations, effective selection and in- per (2), Avakian’s work (3), or any dexing treatment by the conventional other of the 17 cited references which indexing and abstracting services is is relevant to, but does not specifically even more unlikely than it is for the name, citation indexing would open the cited article from Science ( 14). The door to the idea of citation indexing. article in the Journa/ of the Pa/enr Consider the class of readers who Ofice Society ( 17) illustrates one of might have thought about the “idea” the many serious deficiencies of our of a citation index prior to publication fragmented. discipline-oriented index- of this article. They fall into two sub- ing activities (31 ). That paper, on classes—those who might have called indexing chemical patents, was pub- it a citation index or something roughly lished in a legal journal, and thus equivalent, such as a “reference index” the audience of librarians and or “citator,” and those who might not. chemists who might be interested in The latter subclass includes Fano (22) the paper was sacrificed for an audience and Ernst (23), whose linguistic con- of patent attorneys. The situation is ception of the citation-index “idea” was even worse with respect to references quite different from mine, though the 20 and 21, both of which are part end result was essentially the same. of the published proceedings of a con- The semantic difference lies in my ference. Hanson and Jones have shown thinking of a citation index primarily that most papers appearing in the pub- as a printed index, whereas they visu- lished proceedings of conferences are alized a “machine” index. This manipu- never indexed (.32). Since the number 527 of published conference proceedings is The description of a citation index quite large, a considerable amount of does not imply a particular order for important literature would be buried if the list of cited references. We have the participants in these conferences studied in great detail the many ways did not cite the same papers in subse- one can arrange a citation index. These quent articles, published in journals include arrangement by author, jour- which are covered by indexing and ab- nal, year, document serial number, VOl- stracting services. This is reflected in ume, page, or other parameter. Any studies by Touloukian et al. (33) which fragment of the usual citation might show that it is more efficient to use be the basis for organizing a citation an indexing service to locate a few index. The decision to arrange the Sci- recent papers and then search bibliog- ence Citotion Index (8) by author was raphies in these papers than it is to based on a total-systems study in which search the indexes exclusively. it was determined that the typical user The conventional disciplin&oriented requirement is to find what sources have indexes thus leave much to be desired cited a particular reference, albeit at with respect to breadth of coverage times the reference citation is incom- and as means of indexing consistently pletely recollected. Our studies have and by concept. If, instead of search- also shown the desirability of provid- ing for papers on the subject of citation ing, with the citation index, a com- indexes, the reader seeks papers on any plete source index containing full one of dozens of interdisciplinary sub- source-article titles and certain addi- jects investigated today, without know- tional data. This source index is simi- ing the exact headings under which lar to an upgraded conventional author they are indexed, he encounters similar index covering all disciplines—the first difficulties. This will be apparent if, objective of the Unified Science Index for example, he tries to compile rap- (2/). Arrangement by author is fa- idly a bibliography on one of the fol- vored in the citation index and the lowing topics: theories on the origin source index because the research sci- of life: nucleic acid staining techniques; entist usually approaches the literature applications of computers to biomedi- first by author. cal research. By using a citation index one deter- mines what subsequent papers have cited a particular reference. How would What 1s a Citation Index? the new citation index help you find A citation index is an ordered list articles on the subject “citation index”? of cited articles each of which is ac- I have already shown why it would be companied by a list of citing articles. difficult to find these with conventional The citing article is identified by a subject indexes. Suppose you have source citation, the cited article by a found, by chance, the article by Adair reference citation. The index is ar- (}5) by scanning back volumes of ranged by reference citations. Any ,4merican Documentation—a not un- source citation may subsequently be- likely supposition for someone interest- come a reference citation. At the time ed in finding such information. when of indexing, the article you are now you have located the Adair article by reading would be considered a source. such browsing you look it up in a In that case it would appear in the cumulated citation index for the source citation index under all the reference years 1955-64; the index immediately citations in “References and notes” at tells you that at least seven papers the end of the article. It would also have appeared on the subject since 1955 appear in the source index which ac- —14, 17, 19, 21, 24, 26, and the companies the citation index proper. article you are now reading—all citing 528 Adair’s paper! However, this is only not know of a previous work on the the beginning, By a technique called subject he must find one through a “cycling” you can quickly find the other book, an encyclopedia, or a colleague. papers on the subject of citation in- These can usually supply one or more dexes, as weIl as others related to the starting references. If there is little or use of citations. “Cycling” means ex- nothing written on the subject the user amining the bibliographies of the pa- will have a difficult time no matter pers you start with, and of the source what he does, as no literature search papers obtained, in order to locate ad- can turn up what doesn’t exist! ditional relevant works. By looking up the latter in the citation index you find new citing sources. Too Many Citations or Too Few? For example, in my paper in the Chemical Bulletin (19) the letter by Although the average published pa- Schoenbach, in which he criticizes ci- per is cited less than once each year, tat ion indexing, is cited (34). Schoen- certain papers are very frequently cited. bath’s paper in turn refers to my origi- To take an extreme case, the paper nal paper (14), which, through the ci- most frequent] y cited in 1961 was tation index, leads to my reply (35). cited over 500 times (36). While, by Furthermore, by successively checking most search standards, this makes a long on whether the “source” articles which list of citing papers to scan, even this cited Adair have themselves appeared number is not one bit excessive for the later as cited references and following chemist, sociologist, or historian in- up any secondary sources so located, terested in writing a complete review one quickly generates a complete bibli- or evaluation of the method cited. ography. Moreover, several of the citing pa- As the literature of a field increases, pers introduced procedural modifica- the redundancy in bibliographies makes tions. it easier to up-date the search, no mat- It is frequently assumed that the ter which of various related articles is usual citation practices lead to an isn- located first. This redundancy also re- practical number of sources for a par- duces loss of information in the cita- ticular reference. In rare instances this tion index through typographical or oth- may be true, but, as we have seen, er errors, including the omission, un- for certain purposes the searcher may witting or otherwise, of relevant refer- be only too glad to have a rich and ences by authors. comprehensive bibliography to scan, Ex- How can we assume that a searcher perience shows, however, that the num- will find any of the necessary articles ber of sources uncovered is in most to begin his search? The user of the cases quite manageable. Furthermore, citation index must have a starting the yield of sources can be reduced by point. Here is a major difference be- various simple means whenever this is tween conventional subject indexes and required. One such method involves the citation indexes. use of “bibliographic coupling” (28). Proponents of conventional language- In designing the Science Citation in- oriented subject indexes implicitly as- dex (8) it was assumed that the user sume that the typical reader does not could specify one or more references know of any papers on the subject he as starting points. It may sometimes be is investigating. How often is this true necessary or desirable to start with of the working scientist? More often, more than one reference. In these cases perhaps, it is a librarian or student who the searcher can cull the sources by seeks information without prior knowl- looking up in the index only those edge of the subject. If the user does sources which cite two or more of the

529 starting references. This is the essence journals, referees should determine of bibliographic coupling. Or sources whether all pertinent references have may be selected or rejected on the been provided. The citation index will basis of authorship, journal title, article significantly assist the referee in identi- title, number of references, “type” of fying such pertinent references. A pa- article, date of publication, and classi- per recently reported as novel a method fication numbers. of analyzing for peptides (40), even The refining of a search result by though the same work had been re- these methods is generally quite un- ported 4 years earlier (41). There is necessary. In an annual cumulation no question that, had the authors or comprising 1.4 million references (37), referees had access to a citation in- the average number of citing sources dex, the second paper would not have per reference cited was found to be been published, and the subsequent cor- about 1.5. It is easy to lose sight of the rection (42) would have been unneces- fact that, contrary to the general clich6 sary. The two papers (40, 41) con- that there is too much scientific infor- tained four references in common; from mation, there is often little or no infor- any one of these the earlier work could mation available on a specific point have been pinpointed through the cita- (38). The number of references cited tion index. Our files contain numerous each year is a function of the size examples of this type. of the current and past literature and How serious is the problem of non- of the writing habits of the authors. citation of pertinent references, for However, it is interesting to note that whatever reason, by authors? Most of the average number of citing sources us have seen examples of what ap- per ~ference cited did not change ap- pears to be an obvious omission of a preciably once we exceeded a critical reference to a related piece of work by level of several hundred key journals. another author. Such omissions will un- In day-to-day research, the citation doubtedly affect the utility of the cita- index will also provide the scientist tion index for “current awareness” with useful leads toward an unspecified searches. How much cannot yet be de- information objective. Frequently the termined. The fact that papers which scientist-user of indexes does not have do not cite the earlier Literature will a precise objective in mind. He is simply not be retrieved directly through cita- exploring information pathways that ap- tion indexing may exert some influence pear to be exciting and interesting. The on authors in the future. However, citation index facilitates this browsing most papers do contain pertinent bibli- process. On the other hand, the com- ographies, and, in time, most papers are petitive nature of modern research (39) cited a few times. It is a rare paper often involves him in negative Iiterat we which neither cites nor is cited. How- research. Many persons legitimately ever, editors and referees, in accepting hope they will not find pertinent ref- or recommending acceptance of a pa- erences—as, for example, in patent per, might insist that certain standards searches. In evaluating the citation in- of literature search be met by the dex and other indexes one must con- author, just as similar standards are as- sider the ease with which one can ob- sumed by anyone applying for a patent. tain a negative result with a high de- References in patents, however, are sup- gree of certainty. plied by the referee (examiner), not the Obviously citation indexes will be ef- author (inventor). fective only to the extent that the bibliographies in published papers are ac- Dissemination Problem curate reflections of the earlier litera- I have discussed some of the ways ture. In evaluating papers submitted to in which the citation index can be used

530 to search literature. If a printed list examine the array of descriptors gen- of sources which cite a particular ref- erated by all the references cited in a erence is of use, then a service, through particular source paper, How accurate- which such citations, or the articles ly will this list of descriptors describe themselves, are automatically and selec- the contents of the source document? tively disseminated, will also be useful. Some preliminary experiments have re- It is easier to decide how relevant a vealed that the terms selected in index- citing paper is by quickly scanning the ing a source paper corresponded closely paper itself than by reading a title or an with those used to index rhe reference abstract. Through such scanning the citations. The combined array of de- starting reference can be considered in scriptors for all cited articles character- context within the source article. This ized the subject matter of the source step is aided by the fact that most article in great detail. There are cer- citations are enumerated and easily tain exceptions; for example, the no- traced within the body of the text. A menclature used to index a previously sentence or paragraph thus disclosed incompletely described drug is inade- may contain vital information which quate for the subsequently completely had been completely ignored by an identified chemical structure. abstracter or subject indexer. The de- The implications and ramifications of sign of just such an automatic weekly these experiments may prove valuable alerting service has been completed, both in future conventional cerebral in- and indications are that it will sig- dexing and in computer indexing. First, nificantly aid the individual in keeping the speed and consistency of conven- abreast of his specific interests, as de- tional indexing would be increased if fined by his pertinent “question” cita- one could quickly display (by means of tions. computer methods) the earlier indexing terms assigned to the references in a Extensions into Subject Indexhsg particular source article being indexed. What are the possibilities of using This idea was implicit in the Phfico the citation index in conjunction with Medlars proposal (43), in which it conventional indexing? In discussions of was suggested that the indexer would be citation indexes at the Dorking Con- capable of direct communication (on- ference (20) it was correctly concluded line) with the computer. It was also that each reference citation is a form of implied in Fano’s “matrix,” in which index “heading” or descriptor. A simi- the degree of relevance of two docu- lar conclusion was implied in the state- ments is determined by comparing the ment that each author “indexes” his lists of reference citations. In Fano’s own papers each time he cites another system, two documents would be con- paper (14). Now, let us assume that sidered “identical” if the lists of biblio- the ideas expressed in a particular graphical citations were identical. This source article are reflected in the index is a specific case of the more general headings used by some conventional in- axiom that two documents are indis- dexing system. In that case, a display tinguishable within any retrieval system of the descriptors or subject headings if all of the assigned descriptors are the assigned to that paper by the indexer same (44). The only way the docu- constitutes a restatement of the subject ments can be differentiated is by the matter of that paper in the indexer’s assignment of additional descriptors— terminology. When the indexing is au- that is, by indexing in greater depth. tomatic and based on article titles, then the key words restate the title and Machine Citation Index presumably restate the main subjects of If the same magnetic-tape files that the paper, Suppose you now collect and are. used to prepare the nonmanipula-

531 tive printed citation index were searched amples indicating that the scientific by computer, papers could be associat- community is incapable of quickly ab- ed through machine examination of the sorbing radically new ideas or infor- descriptor patterns of cited papers. In mation. If we assume that the papers this way one could incorporate and which have never been cited include utilize existing indexing of earlier pa- those which were ahead of their time, persinmechanically evaluating the rele- the citation index may afford a means vance of source papers. of ferreting out those papers which The machine citation index would al- might deserve reevaluation, redissemi- so facilitate studies on why certain pa- nation, or even republication. One ex- pers are never cited. Kessler reports periment contemplated at the Institute the existence of a large number of such for Scientific Information is the identi- papers (27). What does this signify? fication of genetics papers which were Many factors can contribute to a lack not cited in the Genetics Ci[a~ion in- of citations. In addition to the obvious dex (46). These would be reappraised possibility that a paper is relatively by experts with respect to possible “re- worthless, several information concepts vival” value. It wo~ld be gratifying to come into play. For example, informa- uncover some hitherto uncited papers tion may remain untransmitted if an buried in the literature which, in the article has been published in a relative- light of more recent scientific discover- ly obscure journal, in a journal general- ies, do deserve republication. ly devoted to a~icles in a very different field, or in a language or jargon foreign to potential users. The article may be Citation Indexes and dry or very long, and thus not widely Abstracting Services read. A poorly selected title or bibliography, or both, can also lessen citation Recently Bennett (47) has reiterated of an article. However there is another, my earlier recommendation that an in- and challenging, factor: the timing of dex to the abstracts in specialty jour- a scientific article can be out of step nals and to abstracts prepared by the with the general development of science smaller abstracting services be compiled -out of phase with the general com- (21). Frequently these are abstracts munication network. The “time lag” which include criticism. As such, they can be positive or negative, depending constitute original publications. Every upon the quality or originality of the author should know of such critical ab- message. “Like mutant genes, an idea stracts of his papers. In literature may be before its time—that is, the searches, abstracts may serve in lieu of social climate may not be right for its the original articles, particularly when acceptance” (45). the original article is in a foreign lan- A paper may be so far ahead of its guage, or when it is not readily avail- time that it is not appreciated or cited able. Citation indexes can be used to for many years. Mendel’s experiments locate these abstracts quickly and to with peas in his monastery garden, identify unabstracted articles (31). Fleming’s observations of bacterial lysis in mold-contaminated petri dishes, Pres- Sey’s reports of “An Apparatus Author Citation Index which . . . teaches” all lay buried in A random-access computer memory dusty tomes for decades before their does not require special ordering for vast significance for genetics, antimi- data storage. In such memories the ar- crobial therapy, and teaching machines bitrarily assigned data-addresses need became widely recognized. Indeed, the not be known to the user. By contrast, history of science abounds with ex- a printed citation index must have a

532 logical order. An alphabetical arrange- of orthography has been to have the ment of reference citations by cited computer use less than the author’s ful~ author has definite advantages and dis- name when first identifying two or advantages. One advantage is that an more references to the same citation, author arrangement brings into prox- then to have the computer select one imity references to different works by variation of the cited name for use in the same author. In any other arrange- the index. ment, citations to the work of a single Another complication of the author author would be scattered. A further citation index is the problem of multiple advantage is that the user who re- authorship. If one expects to find cita- members no more than the author’s tions to all the work of a given author, name and the approximate year a paper then that author must appear as the was published can still usually complete primary author in the citations, or the his search. With the author arrange- index must contain cross references or ment there is a small but distinct com- duplicated entries for all co-authors’ plication: the name of a cited author names. The average number of authors may appear with different spellings in per paper now exceeds two (49). To different journals. This problem is ag- list all co-authors in a printed author- gravated by the fact that the scientific citation index would approximately dou- literature employs many languages, al- ble its size. One partial solution to this phabets, and transliterating systems. For cost and space problem has been the instance, when names are transliterated compilation of a separate bibliography from English into Russian and then or index of source articles, with all back into English, the original spelling junior and senior authors listed. Prepa- may be lost. An American named ration of a cumulated cross-referenced Wheeler may come through this mill file based on this source index will as Viiler. Hilbert comes through as Gil- eventually allow the user to quickly bert. Chinese names present even more identify all the works to which a given bizarre examples. To make things author contributed. worse, the Journal of fhe Chemical So- ciefy, and others, drop authors’ initials in citations (48). A Reference to Conclusion Smith, Proc. Chem. Sot. 1953, 1234, is adequate for most purposes. How- The availability of comprehensive ever, specific identification of the author citation indexes now opens new roads is made difficult by this practice. Fortu- to the solution of numerous scientific nately, only a small percentage of cita- and documentation problems. Citation tions present such problems, but these indexing bypasses some of the limita- do increase the cost of processing and tions of classical subject indexing, and the difficulties for the user. One solu- its techniques can be incorporated in tion may ultimately be to prepare brief the existing communication system as “contents pages, ” which contain, for well as in the World Brain, whatever every journal ever published, standard- shape or form that may take. Produc- ized spel Iing of the authors’ names. tion of citation indexes has become an The computer can then be used to re- eminently practicable procedure, and place incomplete, incorrect, or variant the results of research on over 2 mil- spellings with this standardized form. lion citations lead to the conclusion that The preparation of “contents pages” is we cannot afford to neglect this unique also a requisite for the mechanical and versatile instrument, in view of identification of articles which have the accelerating tempo of modern never been cited, discussed earlier. interdisciplinary scientific research. The In compiling the Science Citation in- main objective for the immediate fl t- dex, an interim solution to the problem ture is to increase the coverage, in 533 terms of chronology and number of scientific and related research. To do source publications, so that we will have this will require the support of the a relatively complete inventory of all entire scientific community.

References●nd Notes 19. E. Garfield, “Citation indexes-new paths to scientific knowledge.” Chem. Bull. 43. No. 4. 1. H. G, Wells, world Brain (Doubleday, 11 (1956). - Doran, Gaiden CiIY, NY., 1938). 20. —, in Proceedings of the In(ernatlonal 2. V. Bush, “AS we may think,” ~tlanl~c Study Conference on Classification for ln- Monthly 176, 101 (July, 1945). tormarion Retrieval (Pergamon. New York, 3. E. A. Avakian and E. Garfield, “AMFl8- 1957), p, 98. the Automatic Microfilm Information Sys- 21. —. “A unified index to science.” in tem,” Spec. Libraries 48, 145 ( 1956). Proceedings of the International Conference 4. J. W. Tukey, “Keeping research in contact on Scientific Information, 1958 ( National Academv of Sciences-National Research with the literature: Citation Indices and beyond,” J. Chem. Dec. 2, 34 ( 1962). Council._ Washington, D. C., 1959), PP. 461- 474. 5. J. W. Senders, “Information stora6e requirements for the contents of the world’s li- 22. R. M. Fano, private memorandum ( 1959). braries. ” Science 141, 1067 (1963). 23. H. A. Ernst, “Design and evaluation of a literature retrieval scheme, ” thesis, Massa- During the past 7 years numerous Senate 6. chusetts Institute of Technology ( 1959). hearings on the science-information problem 24. J. W. Tukey, ‘The citation index and the conducted by tbe Committee have been information proble m,” Princeton Univ. Sta- on Government Operations, Subcommittee on tistical Techniques Research Group Ann, Reorganization and International Organiza- Rept. for 1962. tions (Senator Hubert H. Humphrey, chair- 25, 1. R. Savage, Bibliography of Nonparametric man ). See, for example, Interagency CoordL S(aristics ( Harvard Univ. Press. Cambridge. nation o/ information (published pursuant 1962). to Senate Resolution 276, 87th Congress, 21 26. B. Lipetz, “Compilation of an experimental Sept. 1%2) (Government Printing Office, citation index from scientitlc literature, ” Am, Washington, D. C.. 1963). For the House of Dot, 13, 251 ( 1962), Representatives, see, among others, National 27. M. M. Kessler, “Technical information flow Information Center [Hearings on HR. 1946 patterns, ” Proc. Western Joint Computer before the Committee on Education and La- ?on/, ( 1961), PP. 247-257. bor, Ad Hoc Subcommittee on Research 28. —, “Bibliographic coupling between sci- Data Processing and Information Retrieval entific papers,” Am. L30c. 14, 10 (1963). ( Roman Pucinski, chairman) ] (Government 29. P, Atherton and J, C, Yovich, Three E.rperl. Printing Office. Washington. D. C., 1963). ments with Citation index and Bib!iographlc ‘1. A. M, Weinberg ef al., “President’s Science Coupliog of Physics Literature ( American Advisory Committee,” in Science, Govern- In$tllute of Physics. New York, 1962). ment, and Information ( Responsibilities of 30 G. Salton, “Awociative document retrieval the Technical Community in the Transfer of techniques using bibliographic information,” Information ) (Government Printing Office, J, As.voc. Computing Machines 10, 440 (1963). Washington, D. C., 1963). 31 E. Garfield, 1. H. Sher, P, Sopinsky, ‘“Ar. 8. E. Garfield and I. H. Sher, Science Ctfafion title-by-article analysis of abstracting ser- Index ( Institute for Scientific Information, vices, ” Proc, Am. Dec. Insf, (1963), pt. 1, p. Philadelphia. 1963). 45. 9. J. H, Shera and M. E. Egan, Eds,. Bib/io- 32 C, W. Hanson, “Lack of indexes in reports graphic Organization ( Univ. of Chicago of con ferences,” J. Dot, 16, 65 (1960). Press. Chicago. 1951 ). 33 P. S. Lykoudis, P. E. Liley, Y. S. Toul- 10. K. 0’. Murr;, ““History of some attempts to oukian, “Analytical study of a method for organize bibliography internationally, ” in literature search in abstracting journals,” Jn Bibliographic Organization, J. H. Shera and Proceedings of Ihe Internatkmal Conference M. E. Egan, Eds. ( Univ. of Chicago Press, on Scientific Information ( National Academy Chicago, 1951 ), pp. 24-53. of Sciences—National Research Council, 11. E. Garfield, statement and testimony, Hear- Washington, D. C., 1959), vol. 1, pp. 351- ings on H.R, 1946 of 19 July 1963 [see 375; A. O. Cezairliyan, P. S. Lykoudis, Y. S. National Information Center ( Government Touloukian, “Analytical and experimental Printing Office, Washington. D. C.. 1963). study of a method for literature search in PP. 226-2511. abstracting journals,” Thermophysical Prop. 12. J. Maddox, “Is the literature wosth keep- erties Research Center. Purdue Univ.. Rent. i“g?v, Bu//. A/omfc Scientists 19, No. 9, 14 .- No. II (1960). (1963). 34. U. H. Schncnbach, “Citation indexes for 13. J. D,’ “Bernal, “The place of speculation in science,” Science 123, 61 ( 1956). modem technology and science,” in The 35. E. Garfield, “Citation indexed for science.” Scientist Speculate>, 1. J. Good, Ed. (Heine- ibid., p. 62. mann, London, 1963), pp. 11-28. 36. 0. H. Lowry, “Protein measurement with 14. E. Garfield. ‘“Citation indexes for science,* the Folin phenol rea8ent,” J. Biol. Chem. 193, .$ciencc 122, 108 ( 1955). 265 (1951). 15. W, C. Adair, “Citation indexes for scientific 37. E, Garfield, “Citation indexes in sociological literature?”’ Am. Dec. 6, 31 ( 1955). and historical research,” Am. J30c. 14, 289 16. H, C. Hart, “Re: ‘Citation System for (1963), Patent Off ice,’ “ 1. Patent O~ce S0.2. 31, 714 38. S. Hemer, “Technical information—too much (1949). or 100 little?” Sci. Monthly 83, 82 ( 1956). 17. E. Garfield, “Breaking the subject index 39. F. Reif, “The competitive world of the pure barrier—a citation index for chemical scientist, ” Science 134, 1957 ( 1%1). patents,” ibid. 39, 583 ( 1957). 40. R. H. Mazur, B. W, Ellis, p, S, Cam”arah, 18. A. H, Seidel, “Citation system for patent “A new reagent for detection of peptides, office, ” ibid. 31, 554 ( 1949). nucleotides, and other N-H-containing com- Boring, “Dual role of the Zeitgeist in sci- pounds on paper chromatograms,” J. BioL entific creativity, ” SC(. ,440rr/h/y 80, 101 Chem. 237, 1619 (1962). (1955). 41, D. P, Schwartz and M. J. Pallansch, ‘“Tert- 46. E. Garfield and I. H. Sher, Gerrcflcs Citation butyl hypochlorite for detection of nitrog. Index ( Institute for Scientific Information, enous compounds on chromatograms,” Philadelphia, 1963 ). Anal. Chem. 30, 219 (1958). 47. G. Bennett, “Current index to abstracting 42. Correction note, J. BIol. Cherrs. 237, 3315 services,” Sci-Tech News 1S, 129 ( 1961 ) (1962). 48. Since preparation of this article I have 43. Proposal fcu MEDLARS (Philco Corpora- been advised (personal communication, tion Computer Division, Willow Grove, Pa., March 1964) by the editor of the Journal 1961). of the Chemical Sociefy, L. C. Cross, that 44, E. Garfield, “Information theory and other by the end of 1964 authors’ initials will be quantitative factors in code design for docu- included in all reference citations. ment card systems, ” J. Chem. Dec. 1, 70 49. B. L. Clarke, “Multiple authorship trends (1961). in scientific papers,” Science 143, 822 ( 1964). 45. H. Hoagland, “Science and the new human- ism, ” Science 143, 11 I ( 1964); see alSO E. G.

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