Woytinsky, W.S., author
Harper & Brothers, 1957
Buku Teks
Goh, Beng Lan, author
[Publisher not identified], 2002
Artikel Jurnal
Unnithan, T. K. N.
J. B. Wolters-Groningen, 1956
Buku Teks
Mann, E.A.
Sage Publications , 1992
Buku Teks
Jung, Anees, author
Penguin Books, 1997
Buku Teks