SCHEDULE OF INVESTMENTS December 31, 2017

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COMMON STOCKS† - 99.8%

OIL & GAS - 74.1% Exxon Mobil Corp. 12,564 $ 1,050,863 Chevron Corp. 6,989 874,953 ConocoPhillips 8,468 464,809 EOG Resources, Inc. 4,200 453,222 Occidental Petroleum Corp. 5,828 429,290 Phillips 66 3,974 401,970 Valero Energy Corp. 3,955 363,504 Marathon Petroleum Corp. 4,861 320,729 Anadarko Petroleum Corp. 5,912 317,120 Pioneer Natural Resources Co. 1,815 313,723 Transocean Ltd.* 28,568 305,106 Concho Resources, Inc.* 1,804 270,997 Devon Energy Corp. 6,479 268,231 Continental Resources, Inc.* 4,918 260,506 Royal Dutch Shell plc — Class A ADR 3,678 245,359 Andeavor 2,087 238,628 BP plc ADR 5,505 231,375 Apache Corp. 5,466 230,775 Petroleo Brasileiro S.A. ADR* 21,846 224,795 Marathon Oil Corp. 13,209 223,628 Hess Corp. 4,628 219,691 Noble Energy, Inc. 7,510 218,841 Equities Corp. 3,718 211,629 Diamondback Energy, Inc.* 1,652 208,565 Cabot Oil & Gas Corp. — Class A 7,052 201,687 Cimarex Energy Co. 1,614 196,924 Encana Corp. 13,314 177,476 Parsley Energy, Inc. — Class A* 6,010 176,934 HollyFrontier Corp. 3,405 174,404 Suncor Energy, Inc. 4,740 174,053 Helmerich & Payne, Inc.1 2,396 154,877 RSP Permian, Inc.* 3,630 147,668 Newfield Exploration Co.* 4,453 140,403 WPX Energy, Inc.* 9,766 137,408 Energen Corp.* 2,339 134,656 Antero Resources Corp.* 7,040 133,760 Murphy Oil Corp. 4,280 132,894 Centennial Resource Development, Inc. — Class A* 6,570 130,086 Patterson-UTI Energy, Inc. 5,481 126,118 PBF Energy, Inc. — Class A 3,245 115,035 Range Resources Corp. 6,675 113,876 PDC Energy, Inc.* 2,128 109,677 Matador Resources Co.* 3,480 108,332 Canadian Natural Resources Ltd. 2,974 106,231 CNX Resources Corp.* 6,936 101,474 Delek US Holdings, Inc. 2,800 97,832 Diamond Offshore Drilling, Inc.*,1 5,000 92,950 Callon Petroleum Co.* 7,460 90,639 Southwestern Energy Co.* 16,101 89,844 Laredo Petroleum, Inc.* 8,314 88,212 SM Energy Co. 3,968 87,613 Whiting Petroleum Corp.* 3,294 87,225 QEP Resources, Inc.* 8,824 84,446 Kosmos Energy Ltd.* 12,320 84,392 Extraction Oil & Gas, Inc.* 5,844 83,628 Nabors Industries Ltd. 12,046 82,274 Gulfport Energy Corp.* 6,411 81,804 Rowan Companies plc — Class A* 5,207 81,542 SRC Energy, Inc.* 9,317 79,474 Carrizo Oil & Gas, Inc.* 3,421 72,799 Ultra Petroleum Corp.* 8,000 72,480 Oasis Petroleum, Inc.* 8,561 71,998 Halcon Resources Corp.* 7,700 58,289 Total Oil & Gas 12,829,723

OIL & GAS SERVICES - 12.5% Schlumberger Ltd. 8,103 546,061 Halliburton Co. 7,646 373,660 Baker Hughes a GE Co. 10,731 339,529 National Oilwell Varco, Inc. 5,895 212,338 TechnipFMC plc 5,353 167,602 RPC, Inc.1 5,150 131,480 Core Laboratories N.V.1 937 102,648 Oceaneering International, Inc. 3,932 83,123 Dril-Quip, Inc.* 1,607 76,654 McDermott International, Inc.* 10,833 71,281 Superior Energy Services, Inc.* 7,084 68,219 Total Oil & Gas Services 2,172,595

PIPELINES - 10.1% Kinder Morgan, Inc. 19,569 353,612 Williams Companies, Inc. 9,372 285,752 ONEOK, Inc. 4,709 251,696 Cheniere Energy, Inc.* 3,919 210,999 Targa Resources Corp. 3,770 182,543 Enbridge, Inc. 3,654 142,908 Plains GP Holdings, LP — Class A 6,481 142,258 TransCanada Corp. 1,890 91,930 SemGroup Corp. — Class A 3,003 90,691 Total Pipelines 1,752,389

COAL - 1.2% Peabody Energy Corp.* 3,000 118,110 Arch Coal, Inc. — Class A 880 81,981 Total Coal 200,091

METAL FABRICATE & HARDWARE - 0.6% Tenaris S.A. ADR 3,102 98,829

TRANSPORTATION - 0.6% Golar LNG Ltd. 3,212 95,750

MINING - 0.5% US Silica Holdings, Inc. 2,721 88,596

ENERGY-ALTERNATE SOURCES - 0.2% Green Plains, Inc. 2,263 38,131

Total Common Stocks (Cost $8,908,786) 17,276,104 SCHEDULE OF INVESTMENTS (concluded) December 31, 2017

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REPURCHASE AGREEMENTS††,2 - 0.6% JPMorgan Chase & Co. issued 12/29/17 at 1.41% due 01/02/18 $ 72,079 $ 72,079 Bank of America Merrill Lynch issued 12/29/17 at 1.40% due 01/02/18 38,469 38,469 Total Repurchase Agreements (Cost $110,548) 110,548

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SECURITIES LENDING COLLATERAL†,3 - 2.1% Money Market Fund First American Government Obligations Fund — Class Z, 1.15%4 361,857 361,857 Total Securities Lending Collateral (Cost $361,857) 361,857

Total Investments - 102.5% (Cost $9,381,191) $ 17,748,509 Other Assets & Liabilities, net - (2.5)% (430,551) Total Net Assets - 100.0% $ 17,317,958

* Non-income producing security. † Value determined based on Level 1 inputs. †† Value determined based on Level 2 inputs. 1 All or portion of this security is on loan at December 31, 2017. 2 Repurchase Agreements. 3 Securities lending collateral. 4 Rate indicated is the 7 day yield as of December 31, 2017. ADR — American Depositary Receipt plc — Public Limited Company