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 987 97,052 SH   SOLE   97,052 0 0
3M COMPANY COM 88579y101 1,275 6,693 SH   SOLE   6,693 0 0
A. O. SMITH CORPORATION COM 831865209 20,684 484,397 SH   SOLE   484,397 0 0
AAC HOLDINGS INC COM 000307108 227 161,885 SH   SOLE   161,885 0 0
ABBOTT LABORATORIES COM 002824100 826 11,423 SH   SOLE   11,423 0 0
ABBVIE INC SHS COM 00287y109 721 7,822 SH   SOLE   7,822 0 0
ACTIVISION BLIZZARD INC COM 00507v109 2,591 55,632 SH   SOLE   55,632 0 0
AIR PRODUCTS & CHEMICALS, INC. COM 009158106 345 2,158 SH   SOLE   2,158 0 0
ALLEGION PLC COM G0176J109 2,113 26,513 SH   SOLE   26,513 0 0
ALLSTATE CORPORATION COM 020002101 3,128 37,854 SH   SOLE   37,854 0 0
ALPHABET INC CLASS C COM 02079K107 96,880 93,549 SH   SOLE   93,549 0 0
ALPHABET INC. CLASS A COM 02079k305 992 949 SH   SOLE   949 0 0
ALTRIA GROUP INC COM 02209s103 220 4,450 SH   SOLE   4,450 0 0
AMAZON.COM INC COM 023135106 94,985 63,240 SH   SOLE   63,240 0 0
AMERICAN TOWER CORP. COM 03027X100 99,093 626,416 SH   SOLE   626,416 0 0
AMGEN INC COM PV $0.0001 COM 031162100 936 4,806 SH   SOLE   4,806 0 0
ANSYS INC COM 03662Q105 134,416 940,368 SH   SOLE   940,368 0 0
APPLE INC COM 037833100 4,757 30,156 SH   SOLE   30,156 0 0
AUTOMATIC DATA PROC COM 053015103 1,764 13,456 SH   SOLE   13,456 0 0
BANK AMER CORP COM COM 060505104 218 8,861 SH   SOLE   8,861 0 0
BB&T CORPORATION COM 054937107 511 11,793 SH   SOLE   11,793 0 0
BEACON ROOFING SUPPLY INC COM 073685109 1,103 34,764 SH   SOLE   34,764 0 0
BECTON DICKINSON&CO COM 075887109 332 1,475 SH   SOLE   1,475 0 0
BERKLEY W R CORP COM 084423102 2,559 34,625 SH   SOLE   34,625 0 0
BERKSHIRE HATHAWAY INC DELAWA COM 084670108 2,754 9 SH   SOLE   9 0 0
BERKSHIRE HATHAWAY INC CL B COM 084670702 8,506 41,660 SH   SOLE   41,660 0 0
BIO-TECHNE CORP COM 09073M104 74,282 513,280 SH   SOLE   513,280 0 0
BLACK KNIGHT, INC. COM 09215C105 42,801 949,872 SH   SOLE   949,872 0 0
BLACKBAUD INC COM 09227Q100 33,260 528,774 SH   SOLE   528,774 0 0
BLACKLINE, INC. COM 09239B109 109,114 2,664,562 SH   SOLE   2,664,562 0 0
BRIGHT HORIZONS FAM SOL IN DEL COM 109194100 1,768 15,866 SH   SOLE   15,866 0 0
BROOKS AUTOMATION, INC. COM 114340102 61,945 2,366,129 SH   SOLE   2,366,129 0 0
CALAVO GROWERS INC COM 128246105 848 11,625 SH   SOLE   11,625 0 0
CANADIAN NATL RY CO COM COM 136375102 1,482 20,000 SH   SOLE   20,000 0 0
CANTEL MEDICAL CORP COM 138098108 779 10,464 SH   SOLE   10,464 0 0
CAPITAL ONE FINL CORP COM COM 14040H105 2,063 27,296 SH   SOLE   27,296 0 0
CARMAX INC COM 143130102 116,056 1,850,093 SH   SOLE   1,850,093 0 0
CBRE GROUP INC COM 12504L109 59,386 1,483,158 SH   SOLE   1,483,158 0 0
CELGENE CORP COM 151020104 33,900 528,945 SH   SOLE   528,945 0 0
CHEVRON CORP COM 166764100 1,068 9,816 SH   SOLE   9,816 0 0
CHUBB LTD COM h1467j104 383 2,963 SH   SOLE   2,963 0 0
CIGNA CORP COM 125523100 498 2,624 SH   SOLE   2,624 0 0
CISCO SYSTEMS INC COM COM 17275r102 2,687 62,002 SH   SOLE   62,002 0 0
COCA COLA COM COM 191216100 1,828 38,613 SH   SOLE   38,613 0 0
COGENT COMMUNICATIONS COM 19239V302 2,518 55,690 SH   SOLE   55,690 0 0
COLGATE-PALMOLIVE CO COM 194162103 722 12,125 SH   SOLE   12,125 0 0
COMCAST CORP NEW CL A COM 20030n101 5,675 166,679 SH   SOLE   166,679 0 0
CONCHO RES INC COM COM 20605P101 984 9,577 SH   SOLE   9,577 0 0
CONOCOPHILLIPS COM 20825c104 587 9,420 SH   SOLE   9,420 0 0
CONSTELLATION SOFTWARE INC. COM 21037x100 5,281 8,278 SH   SOLE   8,278 0 0
CORE LAB N.V. COM N22717107 31,484 527,730 SH   SOLE   527,730 0 0
COSTAR GROUP INC COM 22160N109 83,299 246,928 SH   SOLE   246,928 0 0
CROWN CASTLE REIT INC SHS COM 22822v101 6,330 58,271 SH   SOLE   58,271 0 0
DANAHER CORP DEL COM COM 235851102 43,221 419,135 SH   SOLE   419,135 0 0
DELTA AIR LINES INC COM 247361702 2,546 51,015 SH   SOLE   51,015 0 0
DEXCOM INC COM 252131107 1,503 12,548 SH   SOLE   12,548 0 0
DIAGEO PLC F ADR COM 25243q205 1,726 12,175 SH   SOLE   12,175 0 0
DISCOVER FINANCIAL SERVICES COM 254709108 4,264 72,292 SH   SOLE   72,292 0 0
DISNEY (WALT) CO COM STK COM 254687106 496 4,522 SH   SOLE   4,522 0 0
DOLLAR GENERAL COM 256677105 5,072 46,930 SH   SOLE   46,930 0 0
DOUGLAS DYNAMICS INC COM 25960R105 2,440 67,979 SH   SOLE   67,979 0 0
DOWDUPONT INC COM 26078j100 306 5,719 SH   SOLE   5,719 0 0
DUKE REALTY CORP REIT COM 264411505 289 11,175 SH   SOLE   11,175 0 0
EAST WEST BANCORP INC COM 27579r104 326 7,500 SH   SOLE   7,500 0 0
ECOLAB INC COM 278865100 172,524 1,170,846 SH   SOLE   1,170,846 0 0
EDWARDS LIFESCIENCES COM 28176e108 2,279 14,881 SH   SOLE   14,881 0 0
ELI LILLY & CO COM 532457108 868 7,503 SH   SOLE   7,503 0 0
ELLIE MAE INC COM 28849P100 427 6,798 SH   SOLE   6,798 0 0
EMERSON ELECTRIC CO COM 291011104 653 10,925 SH   SOLE   10,925 0 0
ENTERPRISE PRDTS PRTN LPL P COM 293792107 1,073 43,617 SH   SOLE   43,617 0 0
ENVESTNET INC COM 29404K106 52,600 1,069,324 SH   SOLE   1,069,324 0 0
EQUITY RESIDENTIAL REIT COM 29476l107 253 3,838 SH   SOLE   3,838 0 0
EVENTBRITE INC COM 29975e109 1,406 50,543 SH   SOLE   50,543 0 0
EVERTEC INC COM 30040P103 753 26,253 SH   SOLE   26,253 0 0
EVO PAYMENT INC COM 26927e104 979 39,687 SH   SOLE   39,687 0 0
EXPONENT INC COM 30214U102 1,690 33,334 SH   SOLE   33,334 0 0
EXXON MOBIL CORP COM COM 30231g102 1,729 25,352 SH   SOLE   25,352 0 0
FACEBOOK INC CLASS COM 30303m102 214 1,632 SH   SOLE   1,632 0 0
FASTENAL CO COM 311900104 125,902 2,407,755 SH   SOLE   2,407,755 0 0
FISERV INC COM 337738108 8,756 119,146 SH   SOLE   119,146 0 0
FORTINET INC COM COM 34959E109 723 10,263 SH   SOLE   10,263 0 0
GENERAL ELECTRIC COM 369604103 505 66,761 SH   SOLE   66,761 0 0
GENESEE AND WYOMING INC COM 371559105 41,545 561,271 SH   SOLE   561,271 0 0
GENUINE PARTS CO COM 372460105 334 3,479 SH   SOLE   3,479 0 0
GUIDEWIRE SOFTWARE INC COM 40171V100 1,339 16,687 SH   SOLE   16,687 0 0
HAMILTON LANE INC COM 407497106 1,260 34,067 SH   SOLE   34,067 0 0
HCP INC COM 40414l109 1,324 47,411 SH   SOLE   47,411 0 0
HD SUPPLY HOLDINGS INC COM 40416M105 2,262 60,297 SH   SOLE   60,297 0 0
HEALTHCARE SERVICES GROUP INC COM 421906108 86,872 2,162,075 SH   SOLE   2,162,075 0 0
HEICO CORP NEW CL A COM 422806208 1,923 30,526 SH   SOLE   30,526 0 0
HELIOS TECHNOLOGIES, INC. COM 866942105 752 22,644 SH   SOLE   22,644 0 0
HOME DEPOT INC COM 437076102 461 2,684 SH   SOLE   2,684 0 0
HONEYWELL INTL INC COM 438516106 2,835 21,459 SH   SOLE   21,459 0 0
IBM CORP COM 459200101 1,075 9,456 SH   SOLE   9,456 0 0
IDEXX LABORATORIES INC COM 45168D104 20,744 111,517 SH   SOLE   111,517 0 0
ILLINOIS TOOL WORKS COM 452308109 263 2,074 SH   SOLE   2,074 0 0
ILLUMINA INC COM 452327109 120,364 401,306 SH   SOLE   401,306 0 0
INTEL CORP COM 458140100 13,530 288,297 SH   SOLE   288,297 0 0
INTUITIVE SURGICAL INC COM 46120E602 103,967 217,086 SH   SOLE   217,086 0 0
JOHN BEAN TECHNOLOGIES COM 477839104 1,261 17,554 SH   SOLE   17,554 0 0
JOHNSON AND JOHNSON COM COM 478160104 14,809 114,757 SH   SOLE   114,757 0 0
JPMORGAN CHASE & CO COM 46625h100 1,962 20,101 SH   SOLE   20,101 0 0
KANSAS CITY SOUTHERN COM NEW COM 485170302 2,271 23,790 SH   SOLE   23,790 0 0
KEYON COMMUNI HOLD INC COM 493312201 0 16,667 SH   SOLE   16,667 0 0
KEYSIGHT TECHNOLOGIES INC COM 49338l103 2,212 35,624 SH   SOLE   35,624 0 0
KIMBERLY CLARK COM 494368103 309 2,713 SH   SOLE   2,713 0 0
LABORATORY CORP AMER HLDGS COM COM 50540R409 2,045 16,187 SH   SOLE   16,187 0 0
LEMAITRE VASCULAR COM 525558201 476 20,127 SH   SOLE   20,127 0 0
LINCOLN NTL CORP IND NPV COM 534187109 534 10,404 SH   SOLE   10,404 0 0
LITHIA MOTORS INC CL A COM 536797103 724 9,486 SH   SOLE   9,486 0 0
LITTELFUSE INC COM 537008104 515 3,006 SH   SOLE   3,006 0 0
LKQ CORP COM 501889208 58,300 2,456,817 SH   SOLE   2,456,817 0 0
LOWE'S COMPANIES INC COM 548661107 3,314 35,877 SH   SOLE   35,877 0 0
LYONDELLBASELL IND N.V. SHS A COM N53745100 769 9,253 SH   SOLE   9,253 0 0
M & T BANK CORP COM 55261f104 473 3,302 SH   SOLE   3,302 0 0
MAGELLAN MIDSTREAM PRTNRS LP C COM 559080106 351 6,151 SH   SOLE   6,151 0 0
MARKEL CORP HLDG CO COM 570535104 91,486 88,133 SH   SOLE   88,133 0 0
MARSH & MC LENNAN COMPANIES IN COM 571748102 960 12,035 SH   SOLE   12,035 0 0
MASTERCARD INC-CLASS A COM 57636Q104 87,151 461,969 SH   SOLE   461,969 0 0
MCCORMICK & CO INC COM NON VTG COM 579780206 1,706 12,255 SH   SOLE   12,255 0 0
MCDONALDS CORP COM COM 580135101 443 2,494 SH   SOLE   2,494 0 0
MERCK AND CO INC SHS COM 58933y105 3,955 51,754 SH   SOLE   51,754 0 0
MESA LABS INC COM 59064R109 1,496 7,180 SH   SOLE   7,180 0 0
MGM RESORTS INTERNATIONAL COM 552953101 1,643 67,710 SH   SOLE   67,710 0 0
MGP INGREDIENTS INC COM 55303J106 771 13,514 SH   SOLE   13,514 0 0
MICROSOFT CORP COM 594918104 10,740 105,741 SH   SOLE   105,741 0 0
MIDDLEBY CORP COM 596278101 1,896 18,455 SH   SOLE   18,455 0 0
MINDBODY INC COM 60255W105 831 22,836 SH   SOLE   22,836 0 0
MONDELEZ INTL INC COM 609207105 1,515 37,850 SH   SOLE   37,850 0 0
MONRO INC COM 610236101 1,397 20,324 SH   SOLE   20,324 0 0
MOODYS CORP COM 615369105 109,704 783,378 SH   SOLE   783,378 0 0
MORGAN STANLEY COM NEW COM 617446448 1,100 27,748 SH   SOLE   27,748 0 0
MSC INDUSTRIAL DIRECT CO INC C COM 553530106 264 3,437 SH   SOLE   3,437 0 0
NEOGEN CORP COM COM 640491106 707 12,400 SH   SOLE   12,400 0 0
NESTLE S A REP RG SH ADR COM 641069406 481 5,942 SH   SOLE   5,942 0 0
NORFOLK SOUTHERN CO COM 655844108 2,661 17,795 SH   SOLE   17,795 0 0
NOVANTA INC COM NPV COM 67000b104 1,411 22,404 SH   SOLE   22,404 0 0
NOVARTIS ADR COM 66987v109 389 4,535 SH   SOLE   4,535 0 0
NUTRIEN LTD COM 67077m108 1,775 37,775 SH   SOLE   37,775 0 0
O REILLY AUTOMOTIVE INC COM 67103H107 17,446 50,667 SH   SOLE   50,667 0 0
OKTA, INC. COM 679295105 33,540 525,712 SH   SOLE   525,712 0 0
ORACLE CORPORATION COM 68389x105 261 5,773 SH   SOLE   5,773 0 0
ORTHOPEDIATRICS CORP COM 68752L100 5,585 160,114 SH   SOLE   160,114 0 0
PAYCHEX INC COM 704326107 3,114 47,792 SH   SOLE   47,792 0 0
PEPSICO INC COM 713448108 1,261 11,411 SH   SOLE   11,411 0 0
PFIZER INC COM 717081103 3,447 78,959 SH   SOLE   78,959 0 0
PHILLIPS 66 COM 718546104 213 2,470 SH   SOLE   2,470 0 0
PINNACLE WEST CAP CORP COM 723484101 256 3,000 SH   SOLE   3,000 0 0
PNC FINCL SERVICES GROUP COM 693475105 1,566 13,394 SH   SOLE   13,394 0 0
POOL CORPORATION COM 73278l105 461 3,098 SH   SOLE   3,098 0 0
PRICE T ROWE GROUP INC COM 74144T108 11,394 123,415 SH   SOLE   123,415 0 0
PROCTER & GAMBLE CO COM 742718109 13,617 148,142 SH   SOLE   148,142 0 0
PROS HOLDINGS INC COM 74346Y103 82,252 2,619,499 SH   SOLE   2,619,499 0 0
PRUDENTIAL FINANCIAL INC COM 744320102 2,021 24,779 SH   SOLE   24,779 0 0
QUALCOMM INC COM 747525103 21,683 381,011 SH   SOLE   381,011 0 0
QUALYS INC COM COM 74758t303 39,387 526,984 SH   SOLE   526,984 0 0
RED HAT INC COM 756577102 100,342 571,295 SH   SOLE   571,295 0 0
REDFIN CORPORATION COM 75737F108 340 23,633 SH   SOLE   23,633 0 0
ROPER TECHNOLOGIES INC COM 776696106 143,158 537,140 SH   SOLE   537,140 0 0
RPM INTERNATIONAL INC COM 749685103 252 4,285 SH   SOLE   4,285 0 0
S & P GLOBAL INC COM 78409V104 92,749 545,773 SH   SOLE   545,773 0 0
SALESFORCE.COM INC COM 79466L302 308 2,248 SH   SOLE   2,248 0 0
SBA COMMUNICATIONS CORP CL A COM 78410G104 44,808 276,782 SH   SOLE   276,782 0 0
SCHLUMBERGER LTD COM 806857108 2,399 66,496 SH   SOLE   66,496 0 0
SEI INVESTMENTS CO COM 784117103 62,504 1,352,907 SH   SOLE   1,352,907 0 0
SERVICE CORP INTL COM 817565104 246 6,100 SH   SOLE   6,100 0 0
SITEONE LANDSCAPE SUPPLY, INC. COM 82982L103 1,282 23,189 SH   SOLE   23,189 0 0
SOUTHERN COMPANY COM 842587107 237 5,399 SH   SOLE   5,399 0 0
STANLEY BLACK & DECK COM 854502101 241 2,010 SH   SOLE   2,010 0 0
STERIS PLC COM G84720104 685 6,407 SH   SOLE   6,407 0 0
TE CONNECTIVITY LTD F COM h84989104 1,992 26,339 SH   SOLE   26,339 0 0
TELADOC INC COM 87918A105 1,569 31,643 SH   SOLE   31,643 0 0
TELEFLEX INC COM COM 879369106 50,736 196,285 SH   SOLE   196,285 0 0
THE BOEING CO COM 097023105 285 884 SH   SOLE   884 0 0
THE DESCARTES SYSTEMS GROUP IN COM 249906108 420 15,891 SH   SOLE   15,891 0 0
THERMO FISHER SCNTFC COM 883556102 18,152 81,110 SH   SOLE   81,110 0 0
TOTAL S.A. COM 89151e109 1,059 20,292 SH   SOLE   20,292 0 0
TRACTOR SUPPLY COMP COM 892356106 1,044 12,508 SH   SOLE   12,508 0 0
TRANSDIGM GROUP INC COM 893641100 86,957 255,712 SH   SOLE   255,712 0 0
TRANSUNION COM 89400j107 18,701 329,251 SH   SOLE   329,251 0 0
TRIMBLE INC COM 896239100 85,940 2,611,377 SH   SOLE   2,611,377 0 0
TYLER TECHNOLOGIES INC COM 902252105 125,381 674,742 SH   SOLE   674,742 0 0
U S BANCORP COM 902973304 1,123 24,579 SH   SOLE   24,579 0 0
ULTIMATE SOFTWARE GROUP INC COM 90385D107 1,046 4,271 SH   SOLE   4,271 0 0
UNILEVER N V N Y SHS NEW COM 904784709 1,565 29,082 SH   SOLE   29,082 0 0
UNION PACIFIC CORP COM 907818108 424 3,065 SH   SOLE   3,065 0 0
UNITED PARCEL SERVICE INC CL B COM 911312106 297 3,041 SH   SOLE   3,041 0 0
UNITED TECHNOLOGIES CORP. COM 913017109 2,498 23,458 SH   SOLE   23,458 0 0
UNITEDHEALTH GRP INC COM 91324p102 1,566 6,285 SH   SOLE   6,285 0 0
VAPOTHERM INC COM 922107107 1,301 65,217 SH   SOLE   65,217 0 0
VENTAS INC REIT COM 92276f100 1,191 20,324 SH   SOLE   20,324 0 0
VERISK ANALYTICS INC COM 92345Y106 156,899 1,438,908 SH   SOLE   1,438,908 0 0
VERIZON COMMUNICATIONS INC COM 92343v104 632 11,241 SH   SOLE   11,241 0 0
VISA INC CL A COM 92826C839 166,540 1,262,238 SH   SOLE   1,262,238 0 0
W.P. CAREY INC. REIT COM 92936u109 333 5,095 SH   SOLE   5,095 0 0
WAGEWORKS INC COM 930427109 18,290 673,434 SH   SOLE   673,434 0 0
WALMART STORES COM 931142103 414 4,441 SH   SOLE   4,441 0 0
WASTE CONNECTIONS INC COM 94106B101 117,233 1,578,890 SH   SOLE   1,578,890 0 0
WATSCO INC COM 942622200 19,849 142,658 SH   SOLE   142,658 0 0
WAYFAIR COM 94419L101 1,625 18,042 SH   SOLE   18,042 0 0
WD-40 COMPANY COM 929236107 1,026 5,601 SH   SOLE   5,601 0 0
WELLS FARGO & CO COM 949746101 236 5,127 SH   SOLE   5,127 0 0
WEYERHAEUSER CO COM 962166104 1,841 84,225 SH   SOLE   84,225 0 0
WSFS FINANCIAL CORP COM 929328102 1,291 34,043 SH   SOLE   34,043 0 0
XPO LOGISTICS INC COM 983793100 1,155 20,241 SH   SOLE   20,241 0 0
BLACKROCK ENHANCED EQT DIV TR ETFS 09251A104 78 10,000 SH   SOLE   10,000 0 0
ISHARES CORE S&P 500 ETF ETFS 464287200 1,569 6,234 SH   SOLE   6,234 0 0
ISHARES CORE S&P MID CAP ETF ETFS 464287507 969 5,834 SH   SOLE   5,834 0 0
ISHARES CORE S&P SMALL CAP ETF ETFS 464287804 645 9,303 SH   SOLE   9,303 0 0
ISHARES MSCI EAFE ETF ETFS 464287465 389 6,626 SH   SOLE   6,626 0 0
ISHARES RUSSELL 2000 GROWTH IN ETFS 464287648 2,192 13,050 SH   SOLE   13,050 0 0
VANGUARD DIVIDEND APPREC ETFS 921908844 1,010 10,309 SH   SOLE   10,309 0 0
VANGUARD FTSE ALL WORLD EX US ETFS 922042775 3,030 66,478 SH   SOLE   66,478 0 0
VANGUARD FTSE EMERGING MARK ET ETFS 922042858 870 22,843 SH   SOLE   22,843 0 0
VANGUARD HIGH DVD YIELD ETF ETFS 921946406 532 6,826 SH   SOLE   6,826 0 0
VANGUARD INDEX FDS FORMERLY VA ETFS 922908363 4,393 19,114 SH   SOLE   19,114 0 0
VANGUARD REIT ETF ETFS 922908553 703 9,425 SH   SOLE   9,425 0 0
VANGUARD TOTAL STK MKT ETF ETFS 922908769 334 2,615 SH   SOLE   2,615 0 0
WISDOMTREE TR INDIA ERNGS FD ETFS 97717W422 223 9,000 SH   SOLE   9,000 0 0