Burt, Robert A.
The Free Press , 1979
Buku Teks
West Publishing Company, 1993
Buku Teks
Ross, Martin J., author
A Fawcett Crest Book, 1967
Buku Teks
Ratliff, Richard C.
The Scarecrow Press,Inc., 1972
Buku Teks
Rodgers, William H., author
St. Paul Minn, 1977
Buku Teks