sumritsakun, chaiyot. “The Analysis of Logistic Costs of Para Rubber Plantation in Chumphon Province”. University of the Thai Chamber of Commerce Journal Humanities and Social Sciences, vol. 40, no. 3, Sept. 2020, pp. 81-94, https://so06.tci-thaijo.org/index.php/utccjournalhs/article/view/241120.