Usher, M.B.
Chapman and Hall , 1973
Buku Teks
Cambridge University Press, 1987
Buku Teks
Hambler, Clive, 1960-
Cambridge University Press , 2013
Buku Teks
editor, John L. Allen
Dushkin/McGraw-Hill, 2000
Buku Referensi
Ananthakrishnan, T.N.
Oxford and IBH, 1982
Buku Teks