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
Estimated average burden
hours per response: 23.8
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
3-D SYS CORP DEL COM NEW COM 88554D205 521 38,940 SH   SOLE   38,940 0 0
3M COMPANY COM 88579y101 1,402 6,680 SH   SOLE   6,680 0 0
AAC HOLDINGS INC COM 000307108 10,298 1,037,024 SH   SOLE   1,037,024 0 0
ABBOTT LABORATORIES COM 002824100 590 11,066 SH   SOLE   11,066 0 0
ABBVIE INC SHS COM 00287y109 683 7,682 SH   SOLE   7,682 0 0
AIR PRODUCTS & CHEMICALS, INC. COM 009158106 275 1,820 SH   SOLE   1,820 0 0
ALPHABET INC CLASS C COM 02079K107 88,388 92,156 SH   SOLE   92,156 0 0
ALPHABET INC. CLASS A COM 02079k305 945 971 SH   SOLE   971 0 0
AMAZON.COM INC COM 023135106 55,287 57,510 SH   SOLE   57,510 0 0
AMERICAN TOWER REIT INC COM 03027X100 90,074 659,016 SH   SOLE   659,016 0 0
AMGEN INC COM PV $0.0001 COM 031162100 262 1,406 SH   SOLE   1,406 0 0
ANSYS INC COM 03662Q105 149,459 1,217,784 SH   SOLE   1,217,784 0 0
APPLE INC COM 037833100 1,403 9,103 SH   SOLE   9,103 0 0
ATRION CORPORATION COM 049904105 6,300 9,375 SH   SOLE   9,375 0 0
AUTOMATIC DATA PROC COM 053015103 1,655 15,138 SH   SOLE   15,138 0 0
BALL CORP COM 058498106 224 5,435 SH   SOLE   5,435 0 0
BEACON ROOFING SUPPLY INC COM 073685109 1,261 24,599 SH   SOLE   24,599 0 0
BECTON DICKINSON&CO COM 075887109 289 1,475 SH   SOLE   1,475 0 0
BERKLEY W R CORP COM 084423102 3,157 47,308 SH   SOLE   47,308 0 0
BERKSHIRE HATHAWAY INC DELAWA COM 084670108 1,648 6 SH   SOLE   6 0 0
BERKSHIRE HATHAWAYINC DEL CL COM 084670702 3,957 21,587 SH   SOLE   21,587 0 0
BIO-TECHNE CORP COM 09073M104 47,839 395,727 SH   SOLE   395,727 0 0
BLACKBAUD INC COM 09227Q100 59,616 678,997 SH   SOLE   678,997 0 0
BLACKLINE COM 09239B109 77,466 2,270,403 SH   SOLE   2,270,403 0 0
BRIGHT HORIZONS FAM SOL IN DEL COM 109194100 967 11,215 SH   SOLE   11,215 0 0
CALAVO GROWERS INC COM 128246105 621 8,489 SH   SOLE   8,489 0 0
CANADIAN NATL RY CO COM COM 136375102 1,657 20,000 SH   SOLE   20,000 0 0
CAPITAL ONE FINL CORP COM COM 14040H105 2,049 24,204 SH   SOLE   24,204 0 0
CARMAX INC COM 143130102 116,673 1,539,022 SH   SOLE   1,539,022 0 0
CARRIAGE SERVICES, INC. COM 143905107 803 31,379 SH   SOLE   31,379 0 0
CARTER'S INC COM 146229109 454 4,602 SH   SOLE   4,602 0 0
CBRE GROUP INC COM 12504L109 39,541 1,043,847 SH   SOLE   1,043,847 0 0
CELGENE CORP COM 151020104 119,542 819,793 SH   SOLE   819,793 0 0
CHEVRON CORP COM 166764100 759 6,456 SH   SOLE   6,456 0 0
CISCO SYSTEMS INC COM COM 17275r102 2,226 66,196 SH   SOLE   66,196 0 0
COCA COLA COM COM 191216100 1,632 36,263 SH   SOLE   36,263 0 0
COGENT COMMUNICATIONS COM 19239V302 1,735 35,481 SH   SOLE   35,481 0 0
COGNIZANT TECHNOLOGY SOLUTIONS COM 192446102 290 4,000 SH   SOLE   4,000 0 0
COLFAX CORPORATION COM 194014106 669 16,055 SH   SOLE   16,055 0 0
COLGATE-PALMOLIVE CO COM 194162103 723 9,925 SH   SOLE   9,925 0 0
COMCAST CORP NEW CL A COM 20030n101 4,095 106,406 SH   SOLE   106,406 0 0
COMPUTER MODELLING LTD COM 205249105 177 24,220 SH   SOLE   24,220 0 0
COMPUTER MODELLING LTD COM 205249105 278 38,020 SH   SOLE   38,020 0 0
CONOCOPHILLIPS COM 20825c104 214 4,284 SH   SOLE   4,284 0 0
CORELOGIC INC COM 21871D103 1,396 30,206 SH   SOLE   30,206 0 0
COSTAR GROUP INC COM 22160N109 88,801 331,040 SH   SOLE   331,040 0 0
CROWN CASTLE REIT INC SHS COM 22822v101 6,635 66,363 SH   SOLE   66,363 0 0
DEXCOM INC COM 252131107 3,711 75,856 SH   SOLE   75,856 0 0
DISCOVER FINANCIAL SERVICES (U COM 254709108 49,681 770,490 SH   SOLE   770,490 0 0
DISNEY (WALT) CO COM STK COM 254687106 1,067 10,826 SH   SOLE   10,826 0 0
DOLLAR GENERAL COM 256677105 233 2,874 SH   SOLE   2,874 0 0
DOUGLAS DYNAMICS INC COM 25960R105 2,502 63,511 SH   SOLE   63,511 0 0
DOWDUPONT INC COM 26078j100 376 5,435 SH   SOLE   5,435 0 0
DUKE REALTY CORP REIT COM 264411505 330 11,450 SH   SOLE   11,450 0 0
DULUTH HOLDINGS INC COM 26443V101 402 19,798 SH   SOLE   19,798 0 0
EAST WEST BANCORP INC COM 27579r104 448 7,500 SH   SOLE   7,500 0 0
ECOLAB INC COM 278865100 154,448 1,200,905 SH   SOLE   1,200,905 0 0
EDWARDS LIFESCIENCES COM 28176e108 1,468 13,431 SH   SOLE   13,431 0 0
ELI LILLY & CO COM 532457108 719 8,408 SH   SOLE   8,408 0 0
ELLIE MAE INC COM 28849P100 4,108 50,017 SH   SOLE   50,017 0 0
EMERSON ELECTRIC CO COM 291011104 795 12,659 SH   SOLE   12,659 0 0
ENTERPRISE PRDTS PRTN LPL P COM 293792107 448 17,175 SH   SOLE   17,175 0 0
ENVESTNET INC COM 29404K106 67,339 1,320,368 SH   SOLE   1,320,368 0 0
EQUITY RESIDENTIAL REIT COM 29476l107 371 5,626 SH   SOLE   5,626 0 0
EVERTEC INC COM 30040P103 436 27,519 SH   SOLE   27,519 0 0
EXPONENT INC COM 30214U102 30,156 408,061 SH   SOLE   408,061 0 0
EXPRESS SCRIPTS HLDG COM 30219g108 1,009 15,941 SH   SOLE   15,941 0 0
EXXON MOBIL CORP COM COM 30231g102 1,624 19,805 SH   SOLE   19,805 0 0
FACEBOOK INC CLASS COM 30303m102 316 1,850 SH   SOLE   1,850 0 0
FASTENAL CO COM 311900104 89,483 1,963,207 SH   SOLE   1,963,207 0 0
FISERV INC COM 337738108 8,712 67,553 SH   SOLE   67,553 0 0
FORTINET INC COM COM 34959E109 368 10,263 SH   SOLE   10,263 0 0
GENERAL ELECTRIC COM 369604103 2,815 116,422 SH   SOLE   116,422 0 0
GENESEE AND WYO INC CL A COM 371559105 11,025 148,965 SH   SOLE   148,965 0 0
GENUINE PARTS CO COM 372460105 480 5,023 SH   SOLE   5,023 0 0
GLACIER BANCORP INC NEW COM 37637Q105 821 21,730 SH   SOLE   21,730 0 0
GUIDEWIRE SOFTWARE INC COM 40171V100 1,396 17,925 SH   SOLE   17,925 0 0
HCP INC COM 40414l109 1,427 51,271 SH   SOLE   51,271 0 0
HEALTHCARE SERVICES GROUP INC COM 421906108 80,996 1,500,765 SH   SOLE   1,500,765 0 0
HEALTHSTREAM INC COM 42222N103 522 22,332 SH   SOLE   22,332 0 0
HEICO CORP NEW CL A COM 422806208 1,681 22,056 SH   SOLE   22,056 0 0
HOME DEPOT INC COM 437076102 415 2,536 SH   SOLE   2,536 0 0
HONEYWELL INTL INC COM 438516106 215 1,520 SH   SOLE   1,520 0 0
IBM CORP COM 459200101 1,026 7,070 SH   SOLE   7,070 0 0
IDEXX LABORATORIES INC COM 45168D104 19,036 122,429 SH   SOLE   122,429 0 0
ILLINOIS TOOL WORKS COM 452308109 303 2,050 SH   SOLE   2,050 0 0
ILLUMINA INC COM 452327109 96,917 486,530 SH   SOLE   486,530 0 0
IMAX CORP COM 45245E109 15,853 699,911 SH   SOLE   699,911 0 0
INTEL CORP COM 458140100 12,344 324,149 SH   SOLE   324,149 0 0
INTUITIVE SURGICAL INC COM 46120E602 137,574 131,539 SH   SOLE   131,539 0 0
JOHN BEAN TECHNOLOGIES COM 477839104 641 6,339 SH   SOLE   6,339 0 0
JOHNSON AND JOHNSON COM COM 478160104 11,018 84,747 SH   SOLE   84,747 0 0
JPMORGAN CHASE & CO COM 46625h100 409 4,280 SH   SOLE   4,280 0 0
KEYON COMMUNI HOLD INC COM 493312201 0 16,667 SH   SOLE   16,667 0 0
KIMBERLY CLARK COM 494368103 278 2,363 SH   SOLE   2,363 0 0
LABORATORY CORP AMER HLDGS COM COM 50540R409 2,693 17,837 SH   SOLE   17,837 0 0
LCI INDUSTRIES COM 50189K103 579 4,996 SH   SOLE   4,996 0 0
LIBERTY TRIPADVISOR HLDGS INC COM 531465102 268 21,717 SH   SOLE   21,717 0 0
LINCOLN NTL CORP IND NPV COM 534187109 820 11,155 SH   SOLE   11,155 0 0
LITHIA MOTORS INC CL A COM 536797103 1,175 9,765 SH   SOLE   9,765 0 0
LITTELFUSE INC COM 537008104 487 2,486 SH   SOLE   2,486 0 0
LKQ CORP COM 501889208 93,492 2,597,715 SH   SOLE   2,597,715 0 0
M & T BANK CORP COM 55261f104 664 4,126 SH   SOLE   4,126 0 0
MAGELLAN MIDSTREAM PRTNRS LP C COM 559080106 256 3,600 SH   SOLE   3,600 0 0
MARKEL CORP HLDG CO COM 570535104 99,180 92,867 SH   SOLE   92,867 0 0
MARKETAXESS HLDGS INC COM COM 57060D108 482 2,610 SH   SOLE   2,610 0 0
MASTERCARD INC-CLASS A COM 57636Q104 68,080 482,152 SH   SOLE   482,152 0 0
MCCORMICK & CO INC COM NON VTG COM 579780206 1,349 13,139 SH   SOLE   13,139 0 0
MERCK AND CO INC SHS COM 58933y105 1,537 24,011 SH   SOLE   24,011 0 0
MESA LABS INC COM 59064R109 1,573 10,536 SH   SOLE   10,536 0 0
MICROSOFT CORP COM 594918104 4,123 55,354 SH   SOLE   55,354 0 0
MIDDLEBY CORP COM 596278101 2,637 20,571 SH   SOLE   20,571 0 0
MONRO INC COM 610236101 1,456 25,974 SH   SOLE   25,974 0 0
MOODYS CORP COM 615369105 133,849 961,489 SH   SOLE   961,489 0 0
MSC INDUSTRIAL DIRECT CO INC C COM 553530106 333 4,407 SH   SOLE   4,407 0 0
NASPERS SPON ADR EACH REP 0.2 COM 631512209 536 12,400 SH   SOLE   12,400 0 0
NATIONAL AMERICAN UNIVER COM 63245q105 32 15,000 SH   SOLE   15,000 0 0
NEOGEN CORP COM COM 640491106 759 9,800 SH   SOLE   9,800 0 0
NESTLE S A REP RG SH ADR COM 641069406 498 5,942 SH   SOLE   5,942 0 0
NORFOLK SOUTHERN CO COM 655844108 302 2,285 SH   SOLE   2,285 0 0
O REILLY AUTOMOTIVE INC COM 67103H107 12,694 58,940 SH   SOLE   58,940 0 0
PAYCHEX INC COM 704326107 3,328 55,511 SH   SOLE   55,511 0 0
PEPSICO INC COM 713448108 637 5,713 SH   SOLE   5,713 0 0
PFIZER INC COM 717081103 1,056 29,567 SH   SOLE   29,567 0 0
PHILIP MORRIS INTL COM 718172109 392 3,533 SH   SOLE   3,533 0 0
PINNACLE WEST CAP CORP COM 723484101 254 3,000 SH   SOLE   3,000 0 0
PIONEER NAT RES CO COM COM 723787107 214 1,449 SH   SOLE   1,449 0 0
PNC FINCL SERVICES GROUP COM 693475105 2,411 17,888 SH   SOLE   17,888 0 0
POOL CORPORATION COM 73278l105 345 3,188 SH   SOLE   3,188 0 0
POTASH CORP SASKATCHEWAN COM 73755l107 590 30,650 SH   SOLE   30,650 0 0
PRA GROUP INC COM 69354N106 245 8,539 SH   SOLE   8,539 0 0
PRICE T ROWE GROUP INC COM 74144T108 12,896 142,264 SH   SOLE   142,264 0 0
PROASSURANCE CORP COM 74267C106 323 5,908 SH   SOLE   5,908 0 0
PROCTER & GAMBLE CO COM 742718109 15,303 168,203 SH   SOLE   168,203 0 0
PROS HOLDINGS INC COM 74346Y103 65,219 2,702,800 SH   SOLE   2,702,800 0 0
QUALCOMM INC COM 747525103 19,841 382,740 SH   SOLE   382,740 0 0
RED HAT INC COM 756577102 168,032 1,515,714 SH   SOLE   1,515,714 0 0
REXNORD CORP COM 76169B102 621 24,429 SH   SOLE   24,429 0 0
ROPER TECHNOLOGIES INC COM 776696106 164,278 674,931 SH   SOLE   674,931 0 0
RPM INTERNATIONAL INC COM 749685103 225 4,385 SH   SOLE   4,385 0 0
S & P GLOBAL INC COM 78409V104 85,097 544,415 SH   SOLE   544,415 0 0
SBA COMMUNICATIONS CORP CL A COM 78410G104 27,437 190,466 SH   SOLE   190,466 0 0
SCHLUMBERGER LTD COM 806857108 6,360 91,173 SH   SOLE   91,173 0 0
SEI INVESTMENTS CO COM 784117103 140,816 2,306,183 SH   SOLE   2,306,183 0 0
SIGNET JEWELERS LTD COM G81276100 685 10,286 SH   SOLE   10,286 0 0
SITEONE COM 82982L103 408 7,028 SH   SOLE   7,028 0 0
SMITH & NEPHEW P L C ADS COM 83175M205 393 10,800 SH   SOLE   10,800 0 0
SOTHERLY HOTELS INC COM COM 83600C103 68 11,625 SH   SOLE   11,625 0 0
SPS COMMERCE INC COM 78463M107 357 6,296 SH   SOLE   6,296 0 0
STERIS PLC COM G84720104 66,609 753,492 SH   SOLE   753,492 0 0
TELADOC INC COM 87918A105 1,700 51,293 SH   SOLE   51,293 0 0
TESLA INC COM 88160R101 231 676 SH   SOLE   676 0 0
THE DESCARTES SYSTEMS GROUP IN COM 249906108 480 17,561 SH   SOLE   17,561 0 0
TRANSDIGM GROUP INC COM 893641100 60,673 237,330 SH   SOLE   237,330 0 0
TRIMBLE INC COM 896239100 95,690 2,437,973 SH   SOLE   2,437,973 0 0
TYLER TECHNOLOGIES INC COM 902252105 104,614 600,129 SH   SOLE   600,129 0 0
U S BANCORP COM 902973304 1,638 30,560 SH   SOLE   30,560 0 0
ULTIMATE SOFTWARE GROUP INC COM 90385D107 528 2,787 SH   SOLE   2,787 0 0
UNITED PARCEL SERVICE INC CL B COM 911312106 377 3,136 SH   SOLE   3,136 0 0
UNITED TECHS CORP COM COM 913017109 467 4,020 SH   SOLE   4,020 0 0
VENTAS INC REIT COM 92276f100 1,917 29,432 SH   SOLE   29,432 0 0
VERISK ANALYTICS INC COM 92345Y106 119,693 1,438,792 SH   SOLE   1,438,792 0 0
VERIZON COMMUNICATNS COM COM 92343v104 457 9,231 SH   SOLE   9,231 0 0
VISA INC CL A COM 92826C839 144,651 1,374,489 SH   SOLE   1,374,489 0 0
W.P. CAREY INC. REIT COM 92936u109 342 5,074 SH   SOLE   5,074 0 0
WABTEC COM 929740108 275 3,626 SH   SOLE   3,626 0 0
WAGEWORKS INC COM 930427109 102,627 1,690,718 SH   SOLE   1,690,718 0 0
WASTE CONNECTIONS INC COM 94106B101 102,097 1,459,368 SH   SOLE   1,459,368 0 0
WATSCO INC COM COM 942622200 69,280 430,125 SH   SOLE   430,125 0 0
WAYFAIR COM 94419L101 566 8,391 SH   SOLE   8,391 0 0
WD-40 COMPANY COM 929236107 656 5,860 SH   SOLE   5,860 0 0
WELLS FARGO & CO COM 949746101 422 7,659 SH   SOLE   7,659 0 0
WELLTOWER INC COM 95040q104 372 5,292 SH   SOLE   5,292 0 0
WSFS FINANCIAL CORP COM 929328102 1,778 36,478 SH   SOLE   36,478 0 0
ZURICH INSURANCE GROUP-ADR COM 989825104 232 7,600 SH   SOLE   7,600 0 0
BLACKROCK ENHANCED EQT DIV TR ETFS 09251A104 91 10,000 SH   SOLE   10,000 0 0
DEUTSCHE X-TRACKERS MSCI EUROP ETFS 233051853 247 8,699 SH   SOLE   8,699 0 0
ISHARES CORE S&P MID CAP ETF ETFS 464287507 1,044 5,834 SH   SOLE   5,834 0 0
ISHARES CORE S&P SMALL CAP ETF ETFS 464287804 683 9,199 SH   SOLE   9,199 0 0
ISHARES MSCI EAFE ETF ETFS 464287465 281 4,099 SH   SOLE   4,099 0 0
VANGUARD DIVIDEND APPREC ETFS 921908844 1,128 11,903 SH   SOLE   11,903 0 0
VANGUARD FTSE ALL WORLD EX US ETFS 922042775 3,507 66,541 SH   SOLE   66,541 0 0
VANGUARD FTSE EMERGING MARK ET ETFS 922042858 904 20,738 SH   SOLE   20,738 0 0
VANGUARD HIGH DVD YIELD ETF ETFS 921946406 826 10,186 SH   SOLE   10,186 0 0
VANGUARD INDEX FDS FORMERLY VA ETFS 922908363 5,305 22,989 SH   SOLE   22,989 0 0
VANGUARD REIT ETF ETFS 922908553 749 9,015 SH   SOLE   9,015 0 0
VANGUARD SHORT-TERM GOV BD ETFS 92206c102 439 7,225 SH   SOLE   7,225 0 0
VANGUARD TOTAL STK MKT ETF ETFS 922908769 339 2,615 SH   SOLE   2,615 0 0
WISDOMTREE TR INDIA ERNGS FD ETFS 97717W422 315 12,500 SH   SOLE   12,500 0 0