Elton, G. R. (Geoffrey Rudolph), author
Cambridge University Press, 1972
Buku Teks
Theen, Rolf H.W, author
Prentice-Hall, 2001
Buku Teks
Cronin, James E., author
Routledge, 1991
Buku Teks
Cullingworth, J.B., author
Allen & Unwin, 1979
Buku Teks
edited by David A. Caputo
W.H. Freeman, 1977
Buku Teks