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Iversen L, Andersen O, Andersen PK, Christoffersen K, Keiding N.Iversen L, et al.Br Med J (Clin Res Ed). 1987 Oct 10;295(6603):879-84. doi: 10.1136/bmj.295.6603.879.Br Med J (Clin Res Ed). 1987.PMID: 3119084Free PMC article.