S., Soegiharto, et al. “Determination of Keystone Species That Influences the Diversity of Birds Species in the Land of Reclamation and Revegetation of Post-Coal Mining”. International Journal of Sciences: Basic and Applied Research (IJSBAR), vol. 35, no. 3, Sept. 2017, pp. 337-4, https://www.gssrr.org/JournalOfBasicAndApplied/article/view/8031.