Cribb, Robert Bridson, author
Longman, 1995
Buku Teks
Kingston, Jeff, 1957-, author
Wiley Blackwell, 2016
Buku Teks
Palmer, R.R. (Robert Roswell), 1909-2002, author
McGraw-Hill, 1992
Buku Teks
Childs, David
Methuen, 1979
Buku Teks
McWilliams, Wayne C., author
Adamantine Press, 1990
Buku Teks