Alfred L. Gardner. Curator of North American mammals and Chief of Mammal Section, National Biological Service, Smithsonian Institution, National Museum of Natural History, Washington, DC, USA
James L. Patton. Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720
Banks, R. C., R. W. McDiarmid, and A. L. Gardner 1987-01-01. Resource Publication, no. 166. United States Department of the Interior Fish and Wildlife Service. Washington, D.C., USA. 79. . .
Wilson, Don E., and Sue Ruff, eds. 1999-01-01. The Smithsonian Book of North American Mammals. Smithsonian Institution Press. Washington, DC, USA. xxv + 750. 1-56098-845-2. .
Wilson, Don E., and DeeAnn M. Reeder, eds. 2005-10-01. Mammal Species of the World: A Taxonomic and Geographic Reference, 3rd ed., vols. 1 & 2. Johns Hopkins University Press. Baltimore, Maryland, USA. 2142. 0-8018-8221-4. .
Wilson, Don E., and DeeAnn M. Reeder, eds. 1992-01-01. Mammal Species of the World: A Taxonomic and Geographic Reference, 2nd ed., 3rd printing. Smithsonian Institution Press. Washington, DC, USA. xviii + 1207. 1-56098-217-9. Corrections were made to text at 3rd printing.
Wilson, Don E., and F. Russell Cole 2000-01-01. Common Names of Mammals of the World. Smithsonian Institution Press. Washington, DC, USA. xiv + 204. 1-56098-383-3. With contributions by Bernadette N. Graham, Adam P. Potter, and Mariana M. Upmeyer.
Wilson & Reeder, eds. (2005): Status: IUCN - Lower Risk (lc)
Wilson & Reeder, eds. (2005): Comments: Subgenus Megascapheus. Revised by Davis (1937) and Rogers (1991a, b), who recognized only two valid subspecies (townsendii and nevadensis). Considered a distinct species by Thaeler (1968b), Patton et al. (1984), Patton and Smith (1989, 1994), and Rogers (1991a, b), despite limited hybridization with bottae in NE California. Hall (1981:469, 495) reviewed Thaeler's evidence and included townsendii in umbrinus (sensu Hall)