1. Ackerknecht EH (1953) Rudolf Virchow: Doctor – statesman – anthropologist. University of Wisconsin Press, Madison
2. Ackerknecht EH (1967) Medicine at the Paris hospital, 1794–1848. Johns Hopkins, Baltimore
3. Ahrens W (1999) Retrospective assessment of occupational exposure in case-control studies. ecomed Verlagsgesellschaft, Landsberg
4. Altman DG, Bland JM (1995) Statistics notes: absence of evidence is not evidence of absence. Br Med J 311:485
5. Bailey NTJ (1975) The mathematical theory of infectious diseases and its applications. Griffin, London