Thomas, Joe G.
Houghton Miffiln, 1990
Buku Teks SO
Winslow, Charles D
The Free Press, 1994
Buku Teks
Rohrer
The New American Library, 1969
Buku Teks SO
McGivering, Ian C.
Liverpool University Press, 1960
Buku Teks SO
Pascale, Richard Tanner
Pustaka Binaman Pressindo , 1992
Buku Teks SO