Daniel, Rick
Delmar, Cengage Learning, 2012
Multimedia
Daniels, Rick
Delmar Cengage Learning, 2012
Buku Referensi
Peter Salim
Modern English Press, 1994
Buku Referensi
Peter Salim
Modern English Press, [date of publication not identified]
Buku Referensi
Arens, William F.
Irwin /McGraw-Hill, 1999
Buku Teks SO