Holloway, William Vernon, author
McGraw-Hill , 1951
Buku Teks
edited by Herbert L. Marx
H.W. Wilson, 1962
Buku Teks
Dye, Thomas R., author
Prentice_Hall, Inc, 1988
Buku Teks
Cox, George, author
Thomson Learning, 2001
Buku Teks
Adrian, Charles R., author
McGraw-Hill , 1978
Buku Teks