de la Torre, S., Snowdon, C.T. and Bejarano, M. (1999) “Preliminary study of the effects of ecotourism and human traffic on the howling behavior of red howler monkeys, Alouatta seniculus, in Ecuadorian Amazonia”, Neotropical Primates, 7(3), pp. 84–86. doi:10.62015/np.1999.v7.431.