Dun & Bradstreet International, 1989
Buku Referensi
edited by Mike Hayhoe and Stephen Parker
Open University Press, 1994
Buku Teks
Clyde, Paul H. (Paul Hibbert), author
Prentice-Hall, 1953
Buku Teks
Walker, Allan S., author
Australian War Memorial, 1956
Buku Teks
edited by Isabel McBryde
Oxford University Press, 1986
Buku Teks