Broto, Carles
Links, [Date of publication not identified]
Buku Referensi
Spens, Michael
Academic Edition, 1995
Buku Teks SO
Arens, William F.
Irwin /McGraw-Hill, 1999
Buku Teks SO
Proffit, William R
Mosby, 2000
Buku Referensi
Meredith, Carol
Rockport Publishers, 2000
Buku Referensi