John, Arlen Hanel. “Individual Behavior Of Female Sumatran Orangutan (Pongo Abelii L.) With Management System In Siantar Zoo”. International Journal of Ecophysiology 3, no. 1 (October 21, 2022): 16–26. Accessed September 10, 2025. https://idjpcr.usu.ac.id/ijoep/article/view/10017.