J. L.  Dew, ?Seed dispersal by two amazonian primates, with notes on dung beetles?, American Zoologist, vol. 39, 1999.

A.  Estrada, A. D., A., and Coates-Estrada, R., ?Tropical rain forest fragmentation, Howler monkeys (Alouatta palliata), and dung beetles at Los Tuxtlas, Mexico?, American Journal of Primatology, vol. 48, pp. 253-262, 1999.

A.  Estrada and Coates-Estrada, R., ?Howler Monkeys Alouatta-Palliata Dung Beetles Scarabaeidae and Seed Dispersal Ecological Interactions in the Tropical Rain Forest of Los Tuxtlas Mexico?, Journal of Tropical Ecology, vol. 7, pp. 459-474, 1991.