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: CITES - Appendix I as H. niger variani; U.S. ESA - Endangered as H. n. variani; IUCN - Critically Endangered as H. n. variani, otherwise Lower Risk (cd)
Wilson & Reeder, eds. (2005): Comments: Includes variani; see Ansell (1972:47). Original publication usually assumed to be Proc. Zool. Soc. Lond., 1838:2 (publ. July, 1838), but McAllan and Bruce (1989) showed that an earlier publication is The Athenaeum (publ. 27 Jan., 1838). Subspecific synonymy follows Ansell (1972:47). In phylogeographic studies, Matthee and Robinson (1999) distinguished niger, kirkii and variani from "roosevelti", and Pitra et al. (2002) recognised clade I ("roosevelti" of Matthee and Robinson, in W Tanzania...