Apter, T.E.
Basingstoke, Hampshire Macmillan 1985,
Buku Teks
Rubinstein, William D.
Routledge, 1997
Buku Teks
Rossi, Peter H., editor
Sage Publications, 1980
Buku Teks
Hart, B. H. Liddell
George Allen and Unwin, 1946
Buku Teks
Gorton, Gary B.
Oxford University Press, 2012
Buku Teks