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| Cityguide AS | Oslo | 2021 |
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| Cityq AS | Sandvika | 2016 |
| Ciupitu G. Ionel Persoana Fizica Autorizata | Ro-050915 City Bucuresti | 2020 |
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| Civil Consulting AS | Asker | 2017 |
| Civil Group AS | Asker | 2019 |
| Civil Management AS | Oslo | 2019 |
| Civita AS | Oslo | 2003 |
| Civitec Engineering AS | Vinterbro | 2025 |
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| CJB AS | Oslo | 2025 |
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| CJB Regnskap AS | Fauske | 2017 |
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| Cjfyys Ltd | Sola | 2010 |
| Cjmjc Ltd | Ab41 9Lj Aberdeenshire | 2022 |
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| CKF AS | Skudeneshavn | 2025 |
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| CKR AS | Tønsberg | 2015 |
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| Claidheamh-Mor Company Ltd | Aberdeen Ab12 5Gb, Scotland | 2019 |
| Claims Survey AS | Færvik | 2011 |
| Clairon AS | Oslo | 2025 |
| Clairon Partners AS | Oslo | 2026 |
| Clairon Y AS | Oslo | 2025 |
| Clairtuv AS | Hosle | 2026 |
| Clan Invest AS | Oslo | 2005 |
| Clandestinjo AS | Oslo | 2017 |
| Claq AS | Tertnes | 2019 |
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| Clarify Holding AS | Fornebu | 2001 |
| Clario AS | Oslo | 2026 |
| Claritas AS | Grimstad | 2023 |
| Clarity AS | Hagan | 2019 |
| Clarkson Hyde Norway AS | Oslo | 2020 |
| Clarkson Port Services BV | 1786Pd Den Helder | 2026 |
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| Clarksons Project Development AS | Oslo | 2020 |
| Clarksons Property Management AS | Oslo | 2010 |
| Clascom AS | Stavanger | 2020 |
| Clashgour Ltd | Inverness-Shire Iv4 7Ej | 2008 |
| Clasima AS | Harestua | 2021 |
| Classica AS | Gamle Fredrikstad | 2024 |
| Claudit AS | Førde | 2024 |
| Claudius Peters Projects GmbH | De-21614 Buxtehude | 2021 |
| Clausen Rekneskap AS | Årdalstangen | 2013 |
| Clausul Da | Oslo | 1990 |
| Clave Consulting AS | Oslo | 2024 |
| Clavia Da | Oslo | 2008 |
| Clavo AS | Sandefjord | 2012 |
| Clawback Aqua AS | Grimstad | 2020 |
| Clawback AS | Oslo | 2004 |
| Clawback Capital AS | Oslo | 2020 |
| Claxton Engineering Services Ltd | Norfolk Nr30 1Ta | 2007 |
| Claypond AS | Oslo | 2022 |
| Clayton Holding AS | Lindesnes | 2023 |
| Cleageye Productions AS | Oslo | 1995 |
| Clean Burn Tech AS | Halden | 2023 |
| Clean Construct Ltd | Oxfordshire Ox11 0Qg | 2026 |
| Clean Energy Group AS | Lysaker | 2012 |
| Clean Energy Solutions AS | Vadsø | 2024 |
| Clean Gas Service AS | Oslo | 2023 |
| Clean Industrial Solutions AS | Oslo | 2022 |
| Clean Metal Processes AS | Gjøvik | 2012 |