Christopher, Dawson
Catholic University of America Press, 20001
Buku Teks
editor, Brian D. Joseph, Richard D. Janda
Blackwell Publishing, 2006
Buku Referensi
Campbell, Lyle
Edinburgh University Press , 2013
Buku Teks
Lehmann, Winfred P.
Holt, Rinehart & Winston, 1973
Buku Teks
Lehmann, Winfred P.
Holt, Rinehart and Winston, 1962
Buku Teks