Davies, Donald W., author
John Wiley & Sons, 1973
Buku Teks
Siswanto Sutojo, author
Damar Mulia Pustaka, 2003
Buku Teks
UNESCO, 1956
Buku Teks
Belch, George E., author
McGraw-Hill, [date of publication not identified]
Buku Referensi
Goodman, David J., author
Addison-Wesley , 1997
Buku Teks