edited by Keith Watson
Croom Helm, 1982
Buku Teks
King, Kenneth, author
Longmann Group, 1991
Buku Teks
Myrdal, Gunnar, 1898-, author
Pantheon Books, 1970
Buku Teks
edited by T.E. Smith
George Allen and Unwin, 1973
Buku Teks
Cammack, Paul Anthony, author
Macmillan, 1993
Buku Teks