Koumpun, Charun, Santi Suksard, Wuthipol Hoamuangkaew, and Chudchawan Sutthissrisinn. 2004. “Recreational Value Assessment of Phuhin Rongkla National Park by Contingent Valuation Method”. Kasetsart Journal of Social Sciences 25 (1):33-43. https://so04.tci-thaijo.org/index.php/kjss/article/view/243371.