Linklater, Andrew, author
Cambridge University Press,, 2006
Buku Teks
editors, Andy Kirkpatrick, Roland Sussex
Springer, 2012
eBooks
Parkinson, Joy, author
Churchill Livingstone, 2004
Buku Teks
Burton, John W.
Macmillan & co. LTD, 1969
Buku Teks
Davison, W. Phillips
N.Y. Praeger , 1965
Buku Teks