Suwanakul, S., and E. J. Wailes. “Estimates of Structural Relationships for the World’s Rubber Market with Particular Emphasis on Thailand’s Natural Rubber Industry”. Kasetsart Journal of Social Sciences, vol. 8, no. 2, July 1987, pp. 173-88, https://so04.tci-thaijo.org/index.php/kjss/article/view/243841.