ASTUTI, PUDJI, et al. “Diurnal Patterns of Testosterone and Cortisol Metabolites in Fecal of Javan Gibbons (Hylobates Moloch) in Captivity”. HAYATI Journal of Biosciences, vol. 13, no. 2, Dec. 2009, p. 69, https://doi.org/10.4308/hjb.13.2.69.