Kongtoei, K. ., S. . Chamnan, and S. . Pruettikul. “Development of Ethical Leadership Indicators for School Principals Under Bangkok Metropolitan Administration”. Academic Journal of Thailand National Sports University, vol. 10, no. 2, May 2018, pp. 237-50, https://he02.tci-thaijo.org/index.php/TNSUJournal/article/view/248640.