Burton, Rosemary, author
Pitman, 1995
Buku Teks
Unwin, Tim, author
Longman Scientific & Technical, 1992
Buku Teks
Thatcher, W.S., author
English University Press, 1957
Buku Teks
Scott, Peter, author
Huytchinson University Library , 1970
Buku Teks
Pounds, Norman J. G., author
McGraw-Hill, 1972
Buku Teks