Fadzim, Wan Roshidah, et al. “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://econjournals.com./index.php/ijefi/article/view/3591.