Whitworth, Michael H., author
Wiley-Blackwell, 2010
Buku Teks
Gray, Richard, 1944-, author
Longman, 1991
Buku Teks
Bogan, Louise, author
Henry Regnery, 1951
Buku Teks
Basic Books, Inc., 1966
Buku Teks
Dembo, L.S., author
University of California Press, 1966
Buku Teks