Não informado. (2007). Report of the Penrose Research Laboratory. Zoological Society of Philadelphia.
Chicago-referens (17:e uppl.)Não informado. Report of the Penrose Research Laboratory. Philadelphia, Pa: Zoological Society of Philadelphia, 2007.
MLA-referens (8:e uppl.)Não informado. Report of the Penrose Research Laboratory. Zoological Society of Philadelphia, 2007.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.