Warangkhana Keerativibool. (2014) Costs and Benefits Gained from Planting Para Rubber in the form of System of Simultaneous Equations: A Case Study of Pa Phayom District, Phatthalung Province and Thung Song District, Nakhon Si Thammarat Province. <i>NIDA Development Journal</i>, <i>54</i>(3), 95-124.Warangkhana Keerativibool. "Costs and Benefits Gained from Planting Para Rubber in the form of System of Simultaneous Equations: A Case Study of Pa Phayom District, Phatthalung Province and Thung Song District, Nakhon Si Thammarat Province". NIDA Development Journal 54 (2014):95-124.Warangkhana Keerativibool. Costs and Benefits Gained from Planting Para Rubber in the form of System of Simultaneous Equations: A Case Study of Pa Phayom District, Phatthalung Province and Thung Song District, Nakhon Si Thammarat Province. National Institute of Development Administration:ม.ป.ท. 2014.