Phainrungruang, R., and P. Lueboonthavatchai. “Interpersonal Problems and Depression of the Elderly at the Elderly Association in Phitsanulok Province”. Journal of the Psychiatric Association of Thailand, vol. 60, no. 1, Aug. 2014, pp. 23-34, https://he01.tci-thaijo.org/index.php/JPAT/article/view/33406.