Senest den 31. december 1991 (forlænget til den 1. juli 1992), med mulighed for under visse betingelser at fastsætte overgangsforanstaltninger indtil den 31. december 1994 (forlænget til den 1. juli 1995).
31 December 1991 at the latest (postponed to 1 July 1992), with the possibility of transitional measures until 31 December 1994 (postponed to 1 July 1995) under certain conditions.