by Stewart Sutherland ... [and others]
Routledge, 1988
Buku Teks SO
edited by Stewart Sutherland, Leslie Houlden, Peter Clarke, Friedhelm Hardy
Routledge, 1988
Buku Referensi
editor, John R. Hinnells
Macmillan, 1993
Buku Referensi
edited by Ian Harris ... [and others]
Longman Current Affairs, 1992
Buku Teks SO
Bettany, G.T.
Bracken Books, [date of publication not identified]
Buku Referensi