1. Cassey, P. & McArdle, B. H. An assessment of distance sampling techniques for estimating animal abundance. Environmetrics 10, 261–278 (1999).
2. Varman, K. S. & Sukumar, R. The line transects method for estimating densities of large mammals in a tropical deciduous forest: an evaluation of models and field experiments. J. Bioscience. 20, 273–287 (1995).
3. Greengrass, E. J. & Maisels, F. Conservation of the Nigerian-Cameroon chimpanzee P. t. vellerosus (and other mammals) in and around the Banyang-Mbo Wildlife Sanctuary, South-west Province, Cameroon. Wildlife Conservation Society, Yaoundé, Cameroon (2007).
4. Maisels, F., Ambahe, E., Ambassa, R., Nyemgah Yara, C. & Fosso, B. Great ape and human impact monitoring in the Mbam et Djerem National park, Cameroon. Final report to USFWS. Wildlife Conservation Society, New York (2009).
5. Groves, C. Primate Taxonomy. Smithsonian Institution Press, Washington, DC, USA (2001).