1. World Population Prospects 2017- Population Division. United Nations. https://esa.un.org/unpd/wpp/Download/Standard/Population/ (Retrieved December 19, 2019).
2. Prasatkul P, Vapattanawong P, Rittirong J, Chuanwan S, Kanchanachitra M, Jaratsit S, Thianlai K, Aruntippaitun S, Mathuam J, Sena K. Situation of the elderly 2017. Bangkok: Institute for Population and Social Research, Mahidol University and Foundation of Thai Gerontology Research and Development Institute (TGRI); 2019. http://thaitgri.org/?wpdmpro=situation-of-the-thai-elderly-2017.
3. Theofilou P. Quality of life: definition and measurement. Eur J Psychol. 2013;9:150–62.
4. Rowe JW, Kahn RL. Successful aging 2.0: conceptual expansions for the 21st century. J Gerontol Ser B Psychol Sci Soc Sci. 2015;70:593–6.
5. World Health Organization. World report on ageing and health. Geneva; 2015. https://www.who.int/ageing/publications/world-report-2015/en/.