Jarvela, Sanna, author
Elsiever, 2011
Buku Teks
Bingham, Tony, author
American Society for Training & Development, 2011
eBooks
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