McWhorter, Kathleen T.
Pearson/Longman, 2007
Buku Teks SO
Wood, Nancy V.
McGraw-Hill, 1991
Buku Teks SO
Smith, Brenda D.
Longman, 2000
Buku Teks SO
Williams, Kate
Macmillan, 1989
Buku Teks
Thomas Nelson and Sons, [Date of publication not identified]
Buku Teks SO