Pursuant to section 9 (1) (a - d) a residence permit can be issued upon application to an alien over the age of 24, cohabiting at a shared resi¬dence, either in marriage or in regular cohabitation of prolonged dura¬tion with a person permanently resident in Denmark over the age of 24, who has obtained a Danish citizenship (a), is a national of one of the other Nordic countries (b), is issued with a residence permit as a refugee (c) or has held a permanent residence permit for Denmark for more than the last 3 years.