Não informado. (1930). Extension service review. Science and Education Administration.
Chicago-referens (17:e uppl.)Não informado. Extension Service Review. Washington: Science and Education Administration, 1930.
MLA-referens (8:e uppl.)Não informado. Extension Service Review. Science and Education Administration, 1930.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.