Intraskul, S., B. Somboonsuke, N. Thongtrai, and P. Phitthayaphinant. “Cost of Para-Rubber Production and Selling Problems of Para-Rubber Farmers in Thailand”. Kasetsart Journal of Social Sciences, vol. 39, no. 3, Dec. 2018, pp. 817-28, https://so04.tci-thaijo.org/index.php/kjss/article/view/242608.