Não informado. (1952). Elementary school science bulletin. National Science Teachers Association.
Chicago-referens (17:e uppl.)Não informado. Elementary School Science Bulletin. Washington: National Science Teachers Association, 1952.
MLA-referens (8:e uppl.)Não informado. Elementary School Science Bulletin. National Science Teachers Association, 1952.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.