Collier, John G. (John Greenwood), author
Cambridge University Pers, 1994
Buku Teks
Rutter, William A., author
s.n., 1973
Buku Teks
Snooks, Graeme Donald
Routledge, 1998
Buku Teks
Parkinson, C. Northcote (Cyril Northcote), 1909-1993, author
Butler & Tanner Ltd, 1962
Buku Teks
Collier, John G. (John Greenwood), author
Cambridge University Press, 1994
Buku Teks