Não informado. (1931). Geological Bulletin. Department of Conservation, Geological Survey.
Chicago-referens (17:e uppl.)Não informado. Geological Bulletin. New Orleans, La: Department of Conservation, Geological Survey, 1931.
MLA-referens (8:e uppl.)Não informado. Geological Bulletin. Department of Conservation, Geological Survey, 1931.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.