Goldston, Eli, author
Carnegie-Mellon University , 1971
Buku Teks
Jarvela, Sanna, author
Elsiever, 2011
Buku Teks
International Association of Gerontology; edited by Clark Tibbitts and Wilma Donahue
Columbia University Press, 1962
Buku Teks
edited by Albert I. Wertheimer and Mickey C. Smith
University Park Press, 1981
Buku Teks
Larkin, Mary, author
McGraw-Hill, 2011
Buku Teks