Italy : International Publications Series, October 1991,
Buku Referensi
edited by William H. Tranter [and others]
Kluwer Academic, 1999
Buku Teks
Lwin, May, author
Bhuana Ilmu Populer, 2005
Buku Teks
Emery, Edwin, editor
Dodd, Mead Company, 1968
Buku Teks
Archer, Robert M., author
Prentice-Hall, 1971
Buku Teks