Não informado. (1911). Contributions from the Princeton University Observatory. Princeton University Observatory.
Chicago-referens (17:e uppl.)Não informado. Contributions from the Princeton University Observatory. Princeton, NJ: Princeton University Observatory, 1911.
MLA-referens (8:e uppl.)Não informado. Contributions from the Princeton University Observatory. Princeton University Observatory, 1911.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.