Hook, Sidney
University of Nebraska Press , 1967
Buku Teks SO
Olmstead, Clifton E.
Prentice-Hall, 1960
Buku Teks SO
Regan, William B.
Harper & Row, 1970
Buku Teks
Bestor, Arthur
Alfred A. Knopf, 1956
Buku Teks
edited by Robert M. Hashway
Praeger, 1990
Buku Referensi