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| Ø.K MASKINDRIFT AS | 918697365 | ØSTRE TOTEN |
| ØKO GRØNT AS | 979908431 | VINJE |
| ØKOHJEM ENTREPRENØR AS | 924527528 | ØVRE EIKER |
| ØKONOMIBYGG ARKITEKTUR AS | 985223769 | OSLO |
| ØKOVENT AS | 912592715 | TRONDHEIM |
| O. KRISTENSEN BYGG AS | 915330940 | SANDNES |
| OKSNES ANLEGG & MASKIN AS | 998533880 | ASKØY |
| ØKSNES ENTREPRENØR AS | 976754301 | ØKSNES |
| OKS-TJENESTER AS | 918598103 | STJØRDAL |
| 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 |
| 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 AGER-WICK AS | 929345223 | ARENDAL |
| OLAV A. VÅGE MASKIN AS | 916941161 | SANDE (MØRE OG ROMSDAL) |
| OLAV ERIK HAGEN AS | 966265949 | STRYN |
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| 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 SOLVANG AS | 976502337 | TOKKE |
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| OLE B. MORK AS | 992115653 | FLATANGER |
| OLE BROR BENTSEN AS | 986368620 | LIER |
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| OLE CHRISTOFFER BRINGEBØEN | 988643424 | LUSTER |
| OLE DAN FUGLESTRAND | 988586927 | GLOPPEN |
| OLE-FREDRIK MOSS | 916940335 | SØR-ODAL |
| OLE F SUHR AS | 997725697 | ALTA |
| OLE GEORG STORUM | 983409709 | BJØRNAFJORDEN |
| 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 |