O`Neil, L. Peat, author
Writer's Digest Books, 1995
Buku Teks
Vaughn, Lewis, author
Oxford , 2006
Buku Teks
Heath, Eric
Prentice-Hall, 1953
Buku Teks
Walters, Roger L., author
McGraw-Hill, 1994
Buku Teks
Vaughn, Lewis, author
Oxford University Press, 2005
Buku Teks