Zulfiandri, Zulfiandri, et al. “The Transformation Process of Cocoa Farmers Groups to Agro-Industry Groups in Indonesia: A Soft System Methodology Approach”. International Journal of Sciences: Basic and Applied Research (IJSBAR), vol. 31, no. 1, Jan. 2017, pp. 1-30, https://gssrr.org/JournalOfBasicAndApplied/article/view/6715.