Gallie, W.B.
Middlesex, Penguin Books, 1952
Buku Teks SO
Ayer, Alfred Jules, 1910-1989
Freeman, Coope, 1968
Buku Teks SO
James, William
Meridian Books , 1959
Buku Teks SO
by Simon Critchle ... [et al.] ; edited by Chantal Mouffe
Routledge, 1996
Buku Teks SO
Roberts, Don D.
Mouton, 1973
Buku Teks SO