Wood, A.W.
Mouton, 1974
Buku Teks
Artikel Jurnal
Macneil, Ian R.
[Publisher not identified], 1966
Buku Teks
edited by Christian P. Potholm and Richard A. Fredland
University Press of America, 1980
Buku Teks SO
Clark, Wilfrid E. Le Gros
Holt, Rinehart and Winston, 1967
Buku Teks