Paolo Janni
The council for research in values and philoaophy, 2001
Buku Teks SO
Khadra, Yasmina
Pustaka Alvabet, 2007
Buku Teks SO
London : Collier-Macmillan, 1967,
Buku Teks
Bonea, Amelia
Oxford University Press, 2016
eBooks
Scott-Ram, N.R.
Cambridge University Press, 1989
Buku Teks