1. United Nations 2020 Report on Ageing.
http://www.un.org/en/sections/issuesdepth/ageing/
2. He, W., Goodkind, D., Kowal, P.: An Aging World: 2015. International Population Reports, Issued in March 2016 by United States Census Bureau (2016)
3. Arslantaş, H., Adana, F., Abacigil Ergin, F., Kayar, D., Acar, G.: Loneliness in elderly people, associated factors and its correlation with quality of life: a field study from Western Turkey. Iran J. Public Health 44(1), 43–50 (2015)
4. Cocarla, A.: Social Isolation and Loneliness in Seniors.
https://srcarecenter.com/article/social-isolation-and-loneliness-in-seniors/
5. Bandari, R., Khankeh, H.R., Shahboulaghi, F.M., Ebadi, A., Keshtkar, A.A., Montazeri, A.: Defining loneliness in older adults: protocol for a systematic review. Syst. Rev. 8, 26 (2019)