Henry F. Howden. 1964.
The Geotrupinae of North and Central America.
Memoirs of the Entomological Society of Canada. 1964. Volume 96. Supplement S39, pp. 5-91.
DOI: 10.4039/entm9639fv, Published online: 31 May 2012
http://journals.cambridge.org/abstract_S0071075X00000746
The file is presented by Jorge Noriega Alvarado in the
Scarab Beetle Taxonomy Discussion List "SCARABS-L@LISTSERV.UNL.EDU".