Haas, Ernst B.
Stanford University Press, 1970
Buku Teks
Holcombe, Arthur N.
New York University press, 1948
Buku Teks
Schenkman Publishing company, 1974
Buku Teks
Selby, David, author
Cambridge University Press, 1988
Buku Teks
Conn Meckler , 1990
Buku Teks