Hughes, Charles W.
Columbia University Press, 1980
Buku Referensi
Pollard, Arthur
Longman, Green, 1960
Buku Teks SO
Simpson, David
Oxford University Press , 1986
Buku Teks SO
Gagey, Edmond M.
Columbia University Press, 1948
Buku Teks SO
edited by Richard Kostelanetz
United States International Communication Agency, 1982
Buku Teks SO