Insin, N., J. Chomchaipol, A. Maliton, A. Chompoochan, N. Wonginta, and T. Singsudee. “Volunteering behaviors and motivation on volunteering of older adults in Amphoe Mueang Sakon Nakhon”. UBRU Journal for Public Health Research, vol. 10, no. 2, Dec. 2021, pp. 118-27, https://he02.tci-thaijo.org/index.php/ubruphjou/article/view/249019.