Key points are not available for this paper at this time.
The article is a short summary of a PhD-thesis, which was accepted by the Faculty of Medicine, University of Copenhagen, May 1989. The thesis is written in Danish with an English summary. It can be obtained free at the Department of General Practice, University of Copenhagen, Juliane Maries Vej 18, DK-2100 København O, Denmark, as long as issues are still available.
Lars Chr. Lassen (Sun,) studied this question.