Comstock, George
Sage Publications, 1991
Buku Teks
Abramson, Albert, author
McFarlan, 2003
Buku Teks
Bernadette Casey.... (et all...)
Routledge , 2008
Buku Teks
Heath, Eric
Prentice-Hall, 1953
Buku Teks
Morley, David, 1964-, author
Routledge, 1992
Buku Teks