Hughes, Edward, author
Pearson Education, 2002
Buku Teks
Hughes, Edward, author
John Wiley & Sons, 1987
Buku Teks
Hughes, Edward, author
Longman, 1995
Buku Teks
Hughes, Edward, author
Longman, 1991
Buku Teks
Baer, Chales J., author
McGraw-Hill, 1980
Buku Teks