Não informado. (1987). Safety & health. National Safety Council.
Chicago-referens (17:e uppl.)Não informado. Safety & Health. Chicago, Ill: National Safety Council, 1987.
MLA-referens (8:e uppl.)Não informado. Safety & Health. National Safety Council, 1987.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.