Levy, John M., author
Prentice-Hall, 1991
Buku Referensi
Branch, Melville C., author
Gadjah Mada University Press, 1995
Buku Teks
Hall, Kenneth B., author
McGraw-Hill, 1995
Buku Teks
Cullingworth, J.B., author
Routledge, 1997
Buku Teks
Lynch, Kevin, author
MIT Press, 1998
Buku Teks