Não informado. (1953). Contributions from the Perkins Observatory. Ohio State University, Ohio Wesleyan University.
Chicago-referens (17:e uppl.)Não informado. Contributions from the Perkins Observatory. Delaware, Ohio: Ohio State University, Ohio Wesleyan University, 1953.
MLA-referens (8:e uppl.)Não informado. Contributions from the Perkins Observatory. Ohio State University, Ohio Wesleyan University, 1953.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.