Lele, Uma
Johns Hopkins, 1975
Buku Teks SO
edited by Michael M. Horowitz and Thomas M. Painter
Westview Press, 1986
Buku Teks SO
Artikel Jurnal
edited by Christian P. Potholm and Richard A. Fredland
University Press of America, 1980
Buku Teks
Macneil, Ian R.
[Publisher not identified], 1966
Buku Teks