Nils Beckman, Margda Waern, Deborah Gustafson, Ingmar Skoog
Beckman N, Waern M, Gustafson D, Skoog I.
Secular trends in self reported sexual activity and satisfaction in Swedish 70 year olds: cross sectional survey of four populations, 1971-2001
BMJ 2008; 337 :a279
doi:10.1136/bmj.a279