King, Chris, author
Longman, 1992
Buku Teks
King, Chris, author
Longman, 1994
Buku Teks
Yardley, Bruce W.D., author
Longman Scientific Technical, 1990
Buku Teks
Hyndmann, Donald W., author
McGraw-Hill, 1985
Buku Teks
Tarbuck, Edward J., author
Maxwell Macmillan, 1993
Buku Teks