Dallas, C. J, Kaewmart N, Detchaiyot P, Phaowiriya H. 2018. “The Effectiveness of Motivational Enhancement Group Therapy Program on Optimism Among Youths With Amphetamine Abuse”. Journal of The Department of Medical Services 43 (5):148-53. https://he02.tci-thaijo.org/index.php/JDMS/article/view/247864.