Surajit Phuphak และ Suwat Terapongtanakorn. (2007) Land Evaluation for Rubber Plantation in Ubon Ratchathani Province. <i>Thai Agricultural Research Journal</i>, <i>25</i>(3), 254-270.Surajit Phuphak และ Suwat Terapongtanakorn. "Land Evaluation for Rubber Plantation in Ubon Ratchathani Province". Thai Agricultural Research Journal 25 (2007):254-270.Surajit Phuphak และ Suwat Terapongtanakorn. Land Evaluation for Rubber Plantation in Ubon Ratchathani Province. Department of Agriculture:ม.ป.ท. 2007.