Fadzim, W. R., M. I. A. Aziz, S. H. C. Mat, and S. Maamor. “Factors Affecting Efficiency of Smallholder Cocoa Farmers: A Tobit Model Application in Malaysia”. International Journal of Economics and Financial Issues, vol. 6, no. 7S, Nov. 2016, pp. 115-9, https://www.econjournals.com/index.php/ijefi/article/view/3591.