Wiwat Wangcharoen, Napaporn Deesanam, Thanes Keokamnerd, and Umaporn Siripin. “Preference Direction Study of Sai Oua by External Preference Mapping and Modified Ratio Profile Test”. Agriculture and Natural Resources, vol. 40, no. 3, June 2006, pp. 721-8, https://li01.tci-thaijo.org/index.php/anres/article/view/243769.