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| ØKONOMIBYGG ARKITEKTUR AS | 985223769 | OSLO |
| O. KRISTENSEN BYGG AS | 915330940 | SANDNES |
| O. KRISTIANSEN ENTREPRENØR AS | 925263052 | ÅSNES |
| OKSNES ANLEGG & MASKIN AS | 998533880 | ASKØY |
| ØKSNES ENTREPRENØR AS | 976754301 | ØKSNES |
| OK TRANSPORT & MASKIN AS | 813874792 | TYSNES |
| O.K. TVEIT AS | 998557712 | KARMØY |
| OK VARMETEKNIKK AS | 994277626 | ØVRE EIKER |
| OK VEDLIKEHOLD AS | 988210595 | AVERØY |
| OK VENTILASJON AS | 968407147 | ÅL |
| OLAF B TERJESEN AS | 936016081 | FÆRDER |
| Olaf E Eriksen AS Entreprenørforretning | 911492377 | OSLO |
| OLA FISKETJØN AS | 966024607 | SULDAL |
| OLAF JOHANSENS EFTF AS | 944685987 | OSLO |
| OLAF O. RUKKE AS | 945665076 | NESBYEN |
| OLAF PETTERSEN AS | 980383644 | HERØY (N.) |
| O LANGSETER & SØNN AS | 926744518 | NORDRE FOLLO |
| OLA RAAEN AS | 948698293 | STJØRDAL |
| OLAV A. VÅGE MASKIN AS | 916941161 | SANDE (MØRE OG ROMSDAL) |
| OLAV ERIK HAGEN AS | 966265949 | STRYN |
| OLAV H HAUSO | 970203532 | ULLENSVANG |
| OLAV HJELMESET AS | 982063337 | GLOPPEN |
| OLAV HOVDE AS | 887832552 | RINGSAKER |
| OLAV KRISTIAN OPPEDAL | 970357947 | LARVIK |
| OLAV LANGLO | 979429967 | TRONDHEIM |
| OLAV LINDSTØL AS | 934031180 | GRIMSTAD |
| OLAV O. HÆREID AS | 948839946 | ÅRDAL |
| OLAV SKARET | 983401686 | GOL |
| OLAV SOLBERG AS | 941579833 | OPPDAL |
| OLAV VENNATRØ AS | 919291184 | STJØRDAL |
| OLDEN RØR AS | 939792686 | STRYN |
| OLE ANDERS BREIDABLIKK | 915741851 | RINGERIKE |
| OLE B. MORK AS | 992115653 | FLATANGER |
| OLE BROR BENTSEN AS | 986368620 | LIER |
| OLE CHRISTIAN ORDERUD | 922036640 | LILLESTRØM |
| OLE CHRISTOFFER BRINGEBØEN | 988643424 | LUSTER |
| OLE DAGSVEEN | 890392032 | LILLEHAMMER |
| OLE DAN FUGLESTRAND | 988586927 | GLOPPEN |
| OLE-FREDRIK MOSS | 916940335 | SØR-ODAL |
| OLE-FREDRIK OLSEN | 927197197 | ÅS |
| OLE HÅKON LOFTHUS AS | 917392366 | ETNEDAL |
| OLEHUS AS | 917570809 | STAVANGER |
| OLE KRISTIAN MOEN | 970393641 | INDRE ØSTFOLD |
| OLE KRISTIAN MORKEN | 914335485 | NORD-FRON |
| OLE M. ALMELI AS | 942657749 | EIDSVOLL |
| OLE MARIUS SKJELIN | 991451277 | SARPSBORG |
| OLE MARKUSSEN OG SØNNER AS | 969013096 | OSTERØY |
| OLE MARTHIN KRISTIANSEN | 971009918 | BAMBLE |
| OLE MARTIN LANNER | 984233639 | LARVIK |
| OLE M DOBLOUG | 979644132 | RINGSAKER |
| ØLEN BETONG AS | 953685124 | VINDAFJORD |
| ØLEN BYGGSERVICE AS | 923048235 | VINDAFJORD |
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| OLE P. BAKKEN AS | 928195678 | HOLTÅLEN |
| OLE PETTER STRØMME AS | 988283142 | VINJE |
| OLE RISTE BYGGEVIRKSOMHET | 970058362 | FJORD |
| OLE SIVERTSEN AS | 817842712 | TRONDHEIM |
| O. LILLEÅS GRUSTAK/TRANSPORT | 990698651 | ORKLAND |
| OLIMB ANLEGG AS | 997409841 | RÅDE |
| OLIMB RØRFORNYING AS | 997447018 | RÅDE |
| OLIVA PARK AS | 920721095 | SARPSBORG |
| O L KYTHE AS | 935252601 | VOSS |
| O.Løkken A/S | 931515829 | TRONDHEIM |
| OLS1 HOLDING AS | 920471129 | LINDESNES |
| OLS1VVS AS | 820951522 | DRAMMEN |
| OLSENBYGG GRIMSTAD AS | 998339898 | GRIMSTAD |
| OLSEN MASKIN & TRANSPORT AS | 919898690 | DØNNA |
| OLSEN RØRLEGGERSERVICE AS | 927532751 | LILLESTRØM |
| OLSET KSU AS | 821996112 | KRISTIANSUND |
| OL TO VVS AS | 983232108 | VENNESLA |
| OLYMPUS VVS AS | 823874642 | OSLO |
| OMA MASKIN | 861758532 | TIME |
| OM BAKKEN BYGG AS | 966707496 | NORD-FRON |
| O&M BYGG AS | 922083134 | BERGEN |
| OMDAL BETONG AS | 912772381 | LILLESAND |
| OMEGA 365 PROTEK AS | 980361330 | KARMØY |
| OMEGA AKERHOLDT AS | 913130529 | ASKER |
| OMEGA BYGG AS | 928978591 | TYSNES |
| OMEGA TDS AS | 991091270 | TØNSBERG |
| ØMF ASKER RINGERIKE AS | 830220852 | ASKER |
| ØMF EVENSEN & EVENSEN AS | 984958552 | LILLEHAMMER |
| ØMF HAMAR AS | 930220760 | HAMAR |
| ØMF ROMERIKE KONGSVINGER AS | 911669668 | KONGSVINGER |
| ØMF WITO AS | 884587832 | EIDSKOG |
| OMGI PRODUCTION AS | 927376695 | TØNSBERG |
| OMHU NORD AS | 933178528 | TROMSØ |
| OMKRI PLAN & ARKITEKTUR AS | 935229871 | TØNSBERG |
| OMLAND MASKIN AS | 990808333 | KVINESDAL |
| OMMEDAL & SØNNER AS | 934033302 | TØNSBERG |
| OM MILJØTEKNIKK AS | 923380701 | BERGEN |
| OMN BYGG AS | 935108160 | ÅLESUND |
| OM SIMONSEN MASKIN AS | 999568033 | MÅLSELV |
| OMT BYGG AS | 933497798 | SUNNFJORD |
| O. MYDLAND MASKIN AS | 984454945 | SOKNDAL |
| ONA CONSULTING AS | 936512585 | STAVANGER |
| ONARHEIM AS | 946471623 | OSLO |
| ON ARKITEKTER OG INGENIØRER AS | 992619295 | ORKLAND |
| ONECO ELEKTRO AS | 996669173 | OSLO |
| ONECO INFRA AS | 997768337 | ARENDAL |