Rippy, J. Fred, author
University of Michigan Press, 1958
Buku Teks
edited by Philip M. Hauser
Unesco, 1961
Buku Teks
Burns, E. Bradford, author
Prentice-Hall, 1977
Buku Teks
Westview Press, 1984
Buku Teks
Lieuwen, Edwin
Frederick A Praeger, 1960
Buku Teks