khayat, P. (2008). The study of elderly health care services in the world. Social Security Journal, 9(4), 99–144.

khayat, P. "The study of elderly health care services in the world", Social Security Journal, 9, 4, 2008, 99–144.

khayat, P. (2008). 'The study of elderly health care services in the world', Social Security Journal, 9(4), pp. 99–144.

khayat, P., "The study of elderly health care services in the world." Social Security Journal, 9 4 (2008): 99–144,

khayat P. The study of elderly health care services in the world. Social Security Journal. 2008;9(4):99–144 (In Persian).