Complete Bibliographic List on Karst Studies: Books: • Gradeshnishka cave. - С.: МТБ, Мед. и физкултура, 1959, 42 с. (in Bulgarian) • Ledenika cave. - С.: МТБ, Мед. и физкултура, 1966, 42 с.; 1968, 43 с. (in Bulgarian) • Pirin. - С.: Наука и изкуство, 1966, 146 с. (in Bulgarian) • Snezhanka. - С.: МТБ, Мед. и физкултура, 1967, 32 с.; 1971, 32 с. (in Bulgarian) • Saeva Dupka cave. - С.: МТБ, Мед. и физкултура, 1969, 36 с.; 1979, 27 с. (in Bulgarian) • Bacho Kiro cave. Киро /Vl. Popov, I. Vaptsarov // - С.: МТБ, Мед. и физкултура, 1972, 32 с. (in Bulgarian) • Geomorphology of the Bulgarian Black Sea Coast. /Vl. Popov, К. Mishev // - С.: БАН, 1974, 268 с. (in Bulgarian) • Ledenika cave - an album. - С.: Мед. и физкултура, 1976, 43 с. (in Bulgarian) • Pirin - guide book. - С.: Мед. и физкултура, 1979, 112 с. (in Bulgarian) • Travels under the ground. - С.: Наука и изк., 1982, 152 с. (in Bulgarian) • Caves with man-made facilities in Bulgaria. - С.: Мед. и физкултура, 1987, 79 с. (in Bulgarian) • Problems of the Bulgarian caves supplied with all necessary facilities. /Vl. Popov, R. Radushev // - С.: Мед. и физкултура, 1989 (in Bulgarian) • Karst morphosculpture - In: Geography of Bulgaria, С.: БАН, 1997; 2002 (in Bulgarian) In periodical and proceedings: • The Bulgarian Black Sea Coast of Dobrudja: geomorphological survey. - Изв. бълг. геогр. д-во, 1953, Т. І (ХІ), 87-108 (in Bulgarian) • The karst in Vrachanska mountain. /К. Mishev, Vl. Popov // - Природа, 1958 (in Bulgarian) • Karst morphology in the region between the valleys of the river Vit and river Batuliiska. - Изв. бълг. геогр. д.во, 1962, Т. ІІІ (ХІІІ), 21-34 (in Bulgarian) • Morphology of the Golemia Kazan cirque in Pirin Mountain. - Изв. Геогр. инст. БАН, 1962, Т. VІ, 85-100 (in Bulgarian) • Morphology and genesis of the Ledenika cave. - Изв. Геогр. инст. БАН, 1964, Т. VІІІ, 77-87 (in Bulgarian) • Karst morphology and karst hydrology in Bulgaria. /Vl. Popov, L. Zjapkov, P. Tranteev // - Пробл. геогр. в НР България. - С.:, 1964, 41-51 (in Bulgarian) • Ice formations in the Ledenika cave. - Изв. Геогр. инст. БАН, 1965, Т. ІХ, 111- 119 (in Bulgarian) • Karst morphology and hydrology in the Fore-Balkan northern part between the rivers Yantra and Osam. /Vl. Zjapkov, P. Penchev, L. Zjapkov // - Изв. Геогр. инст. БАН, 1965, Т. ІХ (ХІХ), 69-91 (in Bulgarian) • Morphology and genesis of the Ledenika cave // Proceedings of the 4th International congress of speleology in Yugoslavia/ T. 3, Ljubljana, 1968, 559- 562 (in Russian). • The karst in the Fore-Balkan northern part between the rivers Iskar and Vit. /Vl. Popov, L. Zjapkov// - Изв. Геогр. инст. БАН, 1969, Т. ХІІ (ХХІІ), 47-59 (in Bulgarian) • Karst distribution in the Stara Planina Mountains and some of its characteristic features. //Geomorphologica Karpato-Balkanica, Krakow, 1970 (in Russian). • Karst distribution in Bulgaria and some of its characteristic features. - Изв. геогр. инст. БАН, 1970, Т. ХІІІ (ХХІІІ), 5-19 (in Bulgarian) • The karst in the northern part of Central Fore-Balkan. /P. Penchev, Vl. Popov, L. Zjapkov// - Пробл. палеогеоморфол. развитие България, С.: БАН, 1971, Т. 1 , 83-91 (in Bulgarian) • Comments on karst denudation in Bulgaria /M. Markowicz, Vl. Popov, M. Pulina// - Geographia Polonika, Warszawa: PAN. 1972, T. 23, 111-139. • Cave zoning in Bulgaria. - Пробл. геогр., 2, 1976, 14-24 (in Bulgarian) • Morphology, genesis and age of the Magura cave. - Пробл. геогр., 1977, 2, 33- 40 (in Bulgarian) • Cave zoning in Bulgaria. - In: Спелеология //Доклади на спелеоложка конф., 10.12.1976 г., София/ С., 1977, 15-31 (in Bulgarian) • Speleogenesis (Magura cave case study). - In: Спелеология //Доклади на спелеоложка конф., 10.12.1976 г., София/ С., 1977, 50-61 (in Bulgarian) • An attempt for characterization of the cave landscapes in Bulgaria. - География, 1978, 16, 15-20 (in Bulgarian) • Fifty years of speleological investigations in Bulgaria. - Пробл. геогр., 1979, 2, 73-74 (in Bulgarian) • Basic terms of karst geomorphology. / Vl. Popov, P. Stefanov // - Пробл. геогр., 1980, 2, 32-42 (in Bulgarian) • Basic terms on karst morphology (calcite and ice karst forms under the ground). - Пробл. геогр., 1980, 4, 73-80 (in Bulgarian) • Geographical cave zoning in Bulgaria. - In: Сб. материали //Европейска регионална конференция по спелеология, 22-28.09.1980 г., София /, T. ІІ, С., 1981, 165-167 (in Russian). • Genesis and age of the Prohodna rock bridge. - Пробл. геогр., 1985, 4, 61-63 (in Bulgarian) • Main approach and principles for elaborating a model of a geomorphological map of Bulgaria, scale 1:400 000. /К. Mishev et all.// - Пробл. геогр., 1986, 4, 3-10 (in Bulgarian) .