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| Siemens D.D. | Hr-10000 Zagreb | 2014 |
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| Siemens Energy | 2750 Ballerup | 2020 |
| Siemens Energy Global GmbH & Co. KG Nuf | De-81739 Munich | 2020 |
| Siemens Energy S.R.L | It-20128 Milano | 2026 |
| Siemens Energy S.R.O. | Cz-61800 Brno-Ziidenice | 2021 |
| Siemens Energy Turbomachinery AS | Kongsberg | 1985 |
| Siemens Gamesa Renewable Energy AS | Oslo | 2016 |
| Siemens Gamesa Renewable Energy Deutschland GmbH Nuf | De-20097 Hamburg | 2025 |
| Siemens Gamesa Renewable Energy Service GmbH | De-20097 Hamburg | 2023 |
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| Sieva Design AS | Maze | 2019 |
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| Sigdal Element Holding AS | Eggedal | 2018 |
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| Sigerfjord Produksjon AS | Sortland | 2023 |
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| Silvergroup Holding AS | Stord | 2020 |
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| Simplicity Finans AS | Vigrestad | 2023 |
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| Simrad AS | Horten | 2007 |
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| Simulatorproduksjon AS | Biri | 2024 |
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| Sinkaberg Invest AS | Rørvik | 2021 |
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| Siriknit AS | Ålesund | 2011 |
| Sirio S.R.L. | 20030 Senago (Mi) | 2016 |
| Sirkull AS | Jar | 2024 |
| Sirkus Renaa Fabrikken AS | Oslo | 2016 |
| Sirmek Holding AS | Sirevåg | 2024 |
| Sirona Dental GmbH | 5071 Wals Bei Salzburg | 2010 |