↑van Roosmalen, Marc G. M., Tomas van Roosmalen, and Russell A. Mittermeier (2002) A Taxonomic Review of the Titi Monkeys, Genus Callicebus Thomas, 1903, With the Description of Two New Species, Callicebus bernhardi and Callicebus stephennashi, from Brazilian Amazonia, Neotropical Primates, vol. 10, supplement June, 2002