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Different rules apply regarding eligibility for Norwegian citizenship for people with residence permits in Norway, people with residence cards for family members of EU/EEA nationals, Nordic nationals and people who have previously been Norwegian citizens.
The applicant is a citizen of : Russian Federation
If you have been a Norwegian citizen, you will normally have had a red Norwegian passport.
There is no separate application form for dual citizenship. When you apply for Norwegian citizenship, you do not need to notify UDI that you want to keep your other citizenship. You can read more about dual citizenship here.