Wittkopf, Eugene R., author
Thomson, 2002
Buku Teks
Alstyne, Richard W. van
Stanford University Press, 1947
Buku Teks
Jones, Howard, author
Franklin Watts, 1985
Buku Teks
Halle, Louis J., author
Harper & Brothers, 1959
Buku Teks
Spanier, John
Frederck A. Praeger, 1968
Buku Teks