The Securities and Exchange Commission has not necessarily reviewed the information in this filing and has not determined if it is accurate and complete.
The reader should not assume that the information is accurate and complete.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 13F

FORM 13F INFORMATION TABLE
OMB APPROVAL
OMB Number: 3235-0006
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COLUMN 1 COLUMN 2 COLUMN 3 COLUMN 4 COLUMN 5 COLUMN 6 COLUMN 7 COLUMN 8
VALUE SHRS OR SH/ PUT/ INVESTMENT OTHER VOTING AUTHORITY
NAME OF ISSUER TITLE OF CLASS CUSIP (x$1000) PRN AMT PRN CALL DISCRETION MANAGER SOLE SHARED NONE
ABB Ltd SPONSORED ADR 000375204 1 49 SH   SOLE   49 0 0
Acuity Brands, Inc. COM 00508Y102 2 15 SH   SOLE   15 0 0
Advanced Energy Industries, Inc. COM 007973100 1 22 SH   SOLE   22 0 0
Albemarle Corporation COM 012653101 4 48 SH   SOLE   48 0 0
Algonquin Power & Utilities COM 015857105 1 114 SH   SOLE   114 0 0
Altus Midstream Company CL A 02215L100 26,268 3,398,174 SH   SOLE   3,398,174 0 0
American Water Works Company, Inc. COM 030420103 11 123 SH   SOLE   123 0 0
Anadarko Petroleum Corp. COM 032511107 7,623 173,880 SH   SOLE   173,880 0 0
Andeavor Logistics, L.P. COM UNIT LP INT 03350F106 476,006 14,650,854 SH   SOLE   13,425,234 0 1,225,620
Antero Midstream G.P., L.P. COM SHS REPSTG 03675Y103 70,305 6,288,465 SH   SOLE   5,859,425 0 429,040
Antero Midstream Partners, L.P. UNT LTD PARTN 03673L103 293,946 13,742,205 SH   SOLE   12,531,019 0 1,211,186
Antero Resources Corp. COM 03674X106 4,412 469,859 SH   SOLE   469,859 0 0
Apache Corp. COM 037411105 1 42 SH   SOLE   42 0 0
Aptiv PLC SHS G6095L109 1 18 SH   SOLE   18 0 0
Aqua America, Inc. COM 03836W103 5 135 SH   SOLE   135 0 0
Aquaventure Holdings Ltd. SHS G0443N107 4 223 SH   SOLE   223 0 0
Atlantica Yield PLC SHS G0751N103 36 1,861 SH   SOLE   1,861 0 0
Autoliv, Inc. COM 052800109 1 8 SH   SOLE   8 0 0
Badger Meter, Inc. COM 056525108 3 53 SH   SOLE   53 0 0
Baker Hughes, a GE Company, L.L.C. CL A 05722G100 1 69 SH   SOLE   69 0 0
BorgWarner, Inc. COM 099724106 2 45 SH   SOLE   45 0 0
BP Midstream Partners, L.P. UNIT LTD PTNR 0556EL109 96,239 6,192,992 SH   SOLE   5,490,936 0 702,056
Brookfield Renewable Energy Partners PARTNERSHIP UNIT G16258108 15 564 SH   SOLE   564 0 0
Buckeye Partners, L.P. UNIT LTD PARTN 118230101 326,772 11,271,876 SH   SOLE   10,344,201 0 927,675
Cabot Oil & Gas Corp. COM 127097103 15,444 690,993 SH   SOLE   690,993 0 0
Cactus, Inc. CL A 127203107 1 19 SH   SOLE   19 0 0
Carrizo Oil & Gas, Inc. COM 144577103 3,083 273,080 SH   SOLE   273,080 0 0
Celanese Corporation COM 150870103 1 16 SH   SOLE   16 0 0
Centennial Resource Development CL A 15136A102 2,394 217,272 SH   SOLE   217,272 0 0
Chart Industries, Inc. COM PAR $0.01 16115Q308 0 7 SH   SOLE   7 0 0
Cheniere Energy, Inc. COM 16411R208 448,076 7,570,124 SH   SOLE   7,313,926 0 256,198
Cheniere Energy Partners, L.P. COM UNIT 16411Q101 1,040 28,797 SH   SOLE   28,797 0 0
Chevron Corp. COM 166764100 2 18 SH   SOLE   18 0 0
Cia Energetica de Minas Gerais SP ADR N-V PFD 204409601 38 10,800 SH   SOLE   10,800 0 0
Cimarex Energy Co. COM 171798101 3,003 48,718 SH   SOLE   48,718 0 0
Clearway Energy, Inc. CL C 18539C204 26 1,514 SH   SOLE   1,514 0 0
Cms Energy Corp. COM 125896100 165 3,322 SH   SOLE   3,322 0 0
CNX Midstream Partners, L.P. COM UNIT REPST 12654A101 82,197 5,048,973 SH   SOLE   5,048,973 0 0
Concho Resources, Inc. COM 20605P101 10,796 105,028 SH   SOLE   105,028 0 0
ConocoPhillips COM 20825c104 3,513 56,344 SH   SOLE   56,344 0 0
Continental Resources, Inc. COM 212015101 10,725 266,868 SH   SOLE   266,868 0 0
Core Laboratories N.V. COM N22717107 1 10 SH   SOLE   10 0 0
Covanta Holding Corporation COM 22282E102 27 2,000 SH   SOLE   2,000 0 0
Danaher Corporation COM 235851102 6 54 SH   SOLE   54 0 0
DCP Midstream, L.P. COM UT LTD PTN 23311P100 73,147 2,761,323 SH   SOLE   2,603,594 0 157,729
Delek Logistics Partners, L.P. COM UNT RP INT 24664T103 7,551 258,162 SH   SOLE   258,162 0 0
Delek US Holdings, Inc. COM 24665A103 9,277 285,354 SH   SOLE   285,354 0 0
Delphi Technologies PLC SHS G2709G107 1 54 SH   SOLE   54 0 0
Devon Energy Corporation COM 25179M103 5,856 259,818 SH   SOLE   259,818 0 0
Diamondback Energy, Inc. COM 25278X109 10,062 108,544 SH   SOLE   108,544 0 0
Dominion Energy, Inc. COM 25746U109 216 3,020 SH   SOLE   3,020 0 0
Dominion Energy Midstream Partners COM UT REP LTD 257454108 48,270 2,013,511 SH   SOLE   1,870,836 0 142,675
Dril-Quip, Inc. COM 262037104 1 20 SH   SOLE   20 0 0
DTE Energy Company COM 233331107 5 41 SH   SOLE   41 0 0
DTE Energy Preferred UNIT 99/99/9999 233331883 2,046 39,600 SH   SOLE   39,600 0 0
Duke Energy Corporation COM 26441C204 3 36 SH   SOLE   36 0 0
Eastman Chemical Co. COM 277432100 1 17 SH   SOLE   17 0 0
Ecolab, Inc. COM 278865100 4 29 SH   SOLE   29 0 0
Edison International COM 281020107 3 49 SH   SOLE   49 0 0
Enbridge, Inc. COM 29250N105 218,989 7,045,980 SH   SOLE   7,045,980 0 0
Energy Recovery, Inc. COM 29270J100 0 72 SH   SOLE   72 0 0
Energy Transfer, L.P. COM UT LTD PTN 29273V100 1,239,060 93,797,153 SH   SOLE   85,682,723 0 8,114,430
Enlink Midstream Partners, L.P. COM UNIT REP LTD 29336U107 185,545 16,852,395 SH   SOLE   15,632,470 0 1,219,925
Enlink Midstream, L.L.C. COM UNIT REP LTD 29336T100 56,071 5,908,479 SH   SOLE   5,908,479 0 0
Ensco PLC SHS CLASS A G3157S106 0 35 SH   SOLE   35 0 0
Enterprise Products Partners, L.P. COM 293792107 1,037,202 42,179,827 SH   SOLE   37,938,424 0 4,241,403
EOG Resources, Inc. COM 26875P101 10,980 125,906 SH   SOLE   125,906 0 0
EQGP Holdings, L.P. COM UNIT REP 26885J103 11,452 574,028 SH   SOLE   574,028 0 0
EQM Midstream Partners, L.P. UNIT LTD PARTN 26885B100 602,649 13,934,084 SH   SOLE   12,602,078 0 1,332,006
EQT Corp. COM 26884L109 21,461 1,136,079 SH   SOLE   1,136,079 0 0
Equitrans Midstream Corporation COM 294600101 111,394 5,564,117 SH   SOLE   5,564,117 0 0
Esco Technologies, Inc. COM 296315104 2 35 SH   SOLE   35 0 0
Evoqua Water Technologies Corp. COM 30057T105 2 243 SH   SOLE   243 0 0
Extraction Oil & Gas, L.L.C. COM 30227M105 1,220 284,405 SH   SOLE   284,405 0 0
Exxon Mobil Corp. COM 30231G102 2 35 SH   SOLE   35 0 0
FireEye, Inc. COM 31816Q101 1 53 SH   SOLE   53 0 0
Ford Motor Co. COM PAR $0.01 345370860 2 207 SH   SOLE   207 0 0
Forum Energy Technologies, Inc. COM 34984V100 0 41 SH   SOLE   41 0 0
FTS International, Inc. COM 30283W104 0 49 SH   SOLE   49 0 0
GasLog Partners, L.P. UNIT LTD PTNRP Y2687W108 44,550 2,250,000 SH   SOLE   2,250,000 0 0
Genesis Energy, L.P. UNIT LTD PARTN 371927104 860 46,539 SH   SOLE   46,539 0 0
Golar LNG Ltd SHS G9456A100 1 25 SH   SOLE   25 0 0
Gulfport Energy Corp. COM 402635304 0 53 SH   SOLE   53 0 0
Halcon Resources Corp COM PAR 40537Q605 1,649 970,000 SH   SOLE   970,000 0 0
Halliburton Company COM 406216101 1 34 SH   SOLE   34 0 0
Hannon Armstrong Sustainable Infrastructure COM 41068X100 38 1,980 SH   SOLE   1,980 0 0
Helmerich & Payne, Inc. COM 423452101 1 20 SH   SOLE   20 0 0
Hess Corp COM 42809H107 1 13 SH   SOLE   13 0 0
Hess Corp DEP PDF SR A 42809H404 2,979 60,000 SH   SOLE   60,000 0 0
Holly Energy Partners, L.P. COM UT LTD PTN 435763107 198,202 6,939,858 SH   SOLE   6,939,858 0 0
Hortonworks, Inc. COM 440894103 1 40 SH   SOLE   40 0 0
IDEX Corporation COM 45167R104 3 20 SH   SOLE   20 0 0
InfraREIT Inc. COM 45685L100 23 1,080 SH   SOLE   1,080 0 0
Itron, Inc. COM 465741106 4 90 SH   SOLE   90 0 0
Keane Group, Inc. COM 48669A108 1 70 SH   SOLE   70 0 0
Kinder Morgan, Inc COM 49456B101 365,721 23,778,981 SH   SOLE   23,105,366 0 673,615
Laredo Petroleum, Inc. COM 516806106 1,203 332,276 SH   SOLE   332,276 0 0
Lear Corporation COM 521865204 0 3 SH   SOLE   3 0 0
Liberty Oilfield Services, Inc. COM CL A 53115L104 0 16 SH   SOLE   16 0 0
Magellan Midstream Partners, L.P. COM UNT RP LP 559080106 926,444 16,236,315 SH   SOLE   14,539,323 0 1,696,992
Magna International, Inc. COM 559222401 2 44 SH   SOLE   44 0 0
Magnolia Oil and Gas Corporation CL A 559663109 1 77 SH   SOLE   77 0 0
Marathon Oil Corp. COM 565849106 2 115 SH   SOLE   115 0 0
Marathon Petroleum Corp. COM 56585A102 3,194 54,120 SH   SOLE   54,120 0 0
Micron Technology, Inc. COM 595112103 2 52 SH   SOLE   52 0 0
Middlesex Water Co. COM 596680108 1 11 SH   SOLE   11 0 0
MiX Telematics Ltd SPONSORED ADR 60688N102 16 1,000 SH   SOLE   1,000 0 0
Monolithic Power Systems, Inc. COM 609839105 4 33 SH   SOLE   33 0 0
MPLX, L.P. COM UNIT REP LTD 55336V100 827,759 27,318,793 SH   SOLE   24,491,850 0 2,826,943
MRC Global, Inc. COM 55345K103 0 27 SH   SOLE   27 0 0
Mueller Water Products, Inc. COM SER A 624758108 3 320 SH   SOLE   320 0 0
National Fuel Gas Co. COM 636180101 1 23 SH   SOLE   23 0 0
NATIONAL OILWELL VARCO INC. COM 637071101 1 22 SH   SOLE   22 0 0
Newfield Exploration Co. COM 651290108 3,072 209,558 SH   SOLE   209,558 0 0
Newpark Resources, Inc. COM PAR $.01 651718504 1 91 SH   SOLE   91 0 0
Nextera Energy, Inc. COM 65339F101 1,404 8,077 SH   SOLE   8,077 0 0
Nextera Energy Partners, L.P. COM UNIT PART IN 65341B106 319 7,410 SH   SOLE   7,410 0 0
Nio, Inc. SPON ADS 62914V106 1 168 SH   SOLE   168 0 0
Nisource, Inc. COM 65473P105 2 64 SH   SOLE   64 0 0
Noble Energy, Inc. COM 655044105 1,453 77,432 SH   SOLE   77,432 0 0
Noble Midstream Partners, L.P. COM UNIT REPST 65506L105 74,905 2,597,272 SH   SOLE   2,358,469 0 238,803
NuStar Energy, L.P. UNIT COM 67058H102 69,905 3,339,960 SH   SOLE   3,339,960 0 0
nVent Electric PLC SHS G6700G107 1 23 SH   SOLE   23 0 0
NVIDIA Corporation COM 67066G104 2 14 SH   SOLE   14 0 0
Occidental Petroleum Corp. COM 674599105 2,740 44,647 SH   SOLE   44,647 0 0
Oceaneering International, Inc. COM 675232102 0 27 SH   SOLE   27 0 0
Olin Corporation COM PAR $1 680665205 1 42 SH   SOLE   42 0 0
ONEOK, Inc. COM 682680103 802,336 14,871,840 SH   SOLE   13,724,274 0 1,147,566
Ormat Technologies, Inc. COM 686688102 2 32 SH   SOLE   32 0 0
Parsley Energy, Inc. CL A 701877102 4,671 292,313 SH   SOLE   292,313 0 0
Pattern Energy Group, Inc. CL A 70338P100 46 2,492 SH   SOLE   2,492 0 0
Patterson-UTI Energy, Inc. COM 703481101 1 64 SH   SOLE   64 0 0
PBF Logistics, L.P. UNIT LTD PTNR 69318Q104 38,984 1,939,498 SH   SOLE   1,939,498 0 0
PDC Energy, Inc. COM 69327R101 1,741 58,500 SH   SOLE   58,500 0 0
Pembina Pipeline Corp. COM 706327103 168,463 5,677,244 SH   SOLE   5,677,244 0 0
Pentair plc SHS G7S00T104 5 129 SH   SOLE   129 0 0
Phillips 66 Partners, L.P. COM UNIT REP INT 718549207 466,731 11,083,615 SH   SOLE   10,005,860 0 1,077,755
Pioneer Natural Resources Co. COM 723787107 12,140 92,308 SH   SOLE   92,308 0 0
Plains All American Pipeline, L.P. UHNIT LTD PARTN 726503105 779,205 38,882,509 SH   SOLE   34,019,370 0 4,863,139
Plains GP Holdings, L.P. LTD PARTNR INT A 72651A207 197,859 9,843,712 SH   SOLE   9,843,712 0 0
PPL Corporation COM 69351T106 3 96 SH   SOLE   96 0 0
QEP Resources, Inc. COM 74733V100 0 68 SH   SOLE   68 0 0
Range Resources Corp. COM 75281A109 4,487 468,860 SH   SOLE   468,860 0 0
Schlumberger, Ltd. COM 806857108 2 66 SH   SOLE   66 0 0
Select Energy Services, Inc. CL A COM 81617J301 0 28 SH   SOLE   28 0 0
Semgroup Corp CL A 81663A105 66,887 4,853,930 SH   SOLE   4,853,930 0 0
Sempra Energy COM 816851109 233 2,155 SH   SOLE   2,155 0 0
Sempra Energy 6% PFD CONV A 816851406 4,756 50,000 SH   SOLE   50,000 0 0
Shell Midstream Partners, L.P. UNIT LTD INT 822634101 340,881 20,772,749 SH   SOLE   19,348,975 0 1,423,774
SM Energy Co. COM 78454L100 1,364 88,100 SH   SOLE   88,100 0 0
Splunk, Inc. COM 848637104 1 8 SH   SOLE   8 0 0
Sunrun, Inc. COM 86771W105 3 294 SH   SOLE   294 0 0
Superior Energy Services, Inc. COM 868157108 0 74 SH   SOLE   74 0 0
Tallgrass Energy, L.P. CLASS A SHS 874696107 584,470 24,012,755 SH   SOLE   22,320,249 0 1,692,506
Targa Resources Corp. COM 87612G101 349,377 9,699,540 SH   SOLE   9,129,485 0 570,055
TechnipFMC PLC COM G87110105 1 37 SH   SOLE   37 0 0
Terraform Power, Inc. COM CL A 88104R209 37 3,299 SH   SOLE   3,299 0 0
Tesla, Inc. COM 88160R101 9 26 SH   SOLE   26 0 0
Tetra Tech, Inc. COM 88162G103 3 51 SH   SOLE   51 0 0
The Goodyear Tire & Rubber Company COM 382550101 1 41 SH   SOLE   41 0 0
The York Water Co. COM 987184108 0 15 SH   SOLE   15 0 0
Tortoise North American Pipeline TORTOISE NRAM PI 56167N720 21,053 1,057,431 SH   SOLE   1,057,431 0 0
Transcanada Corp. COM 89353D107 223,167 6,251,175 SH   SOLE   6,251,175 0 0
Transocean Ltd. REG SHS H8817H100 0 40 SH   SOLE   40 0 0
USA Compression Partners, L.P. COMUNIT LTDPAR 90290N109 0 33 SH   SOLE   33 0 0
Valero Energy Corp. COM 91913Y100 10,271 137,002 SH   SOLE   137,002 0 0
Valero Energy Partners, L.P. COM UNT REP LP 91914J102 1,645 39,014 SH   SOLE   39,014 0 0
Veoneer, Inc. COM 92336X109 0 8 SH   SOLE   8 0 0
Verisk Analytics, Inc. COM 92345Y106 1 10 SH   SOLE   10 0 0
Vistra Energy Corp. COM 92840M102 1 63 SH   SOLE   63 0 0
Watts Water Technologies, Inc. CL A 942749102 2 28 SH   SOLE   28 0 0
WEC Energy Group, Inc. COM 92939U106 248 3,584 SH   SOLE   3,584 0 0
Western Gas Equity Partners, L.P. COMUNT LTD PT 95825R103 87,740 3,164,071 SH   SOLE   2,771,132 0 392,939
Western Gas Partners, L.P. COM UNIT LP IN 958254104 666,354 15,779,164 SH   SOLE   14,264,928 0 1,514,236
Westlake Chem Corp. COM 960413102 1 21 SH   SOLE   21 0 0
Whiting Petroleum Corp. COM 966387409 1,462 64,430 SH   SOLE   64,430 0 0
Williams Companies, Inc. COM 969457100 841,185 38,148,968 SH   SOLE   35,269,983 0 2,878,985
WPX Energy, Inc. COM 98212B103 7,339 646,593 SH   SOLE   646,593 0 0
Xylem, Inc. COM 98419M100 11 166 SH   SOLE   166 0 0