Crane, Donald P.
Kent publishing company, 1986
Buku Teks
Sikula, Andrew F., author
John Weley, 1984
Buku Teks
French, Wendell
Houghton Mifflin, 1974
Buku Teks
Jackson, Susan E., author
South Westh Western College, 2000
Buku Teks
Storey, John, 1950-, author
Blackwell, 1992
Buku Teks