edited by Susan L. Feagin and Patrick Mayhard
Oxford University Press, 1997
Buku Teks SO
Osborne, Harold
London Routledge & Kegan Paul 1955
Buku Teks
essays by W.B. Gallie ... [and others] ; edited by William Elton
Blackwell, 1954
Buku Teks SO
Graham, Gordon
Routledge, 1997
Buku Teks SO
Hubbard, L. Ron, 1911-1986
Bridge Publications, 2012
Buku Referensi