Butts, R. Freeman
Beacon Press, 1950
Buku Teks
Hook, Sidney, author
University of Nebraska Press , 1967
Buku Teks
Olmstead, Clifton E., author
Prentice-Hall, 1960
Buku Teks
Regan, William
Harper & Row, Publishers, 1970
Buku Teks
Bestor, Arthur
Knopf, 1956
Buku Teks