Não informado. (1977). Vital and health statistics. National Center for Health Statistics.
Chicago-referens (17:e uppl.)Não informado. Vital and Health Statistics. Washington: National Center for Health Statistics, 1977.
MLA-referens (8:e uppl.)Não informado. Vital and Health Statistics. National Center for Health Statistics, 1977.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.