Hewings, Martin
Advanced grammar in use : a reference and practice book for advanced students of english
Cambridge University Press, 2005
 Buku Teks SO
Some grammatical errors made by the students of Unpam
 Artikel Jurnal
McCarthy, Michael
English vocabulary in use : upper-intermediate & advanced
Erlangga, 2002
 Buku Teks SO
Azar, Betty Schrampfer, 1941-
Basic english grammar
Prentice Hall Regents, 1995
 Buku Teks SO
Azar, Betty Schrampfer, 1941-
Fundamentals of English grammar / Betty Schrampfer Azar ; Barbara Matthies
Prentice-Hall, 1985
 Buku Teks SO