Cheney, L.J, author
The New American Library , 1959
Buku Teks
edited by Year
Oxford Paper, 1956
Buku Teks
Revill, J.C.
Longmans, 1959
Buku Teks
Smart, Terry L., author
Holt, Reinhart and Winston, 1987
Buku Teks
London Chancellor Press 1999,
Buku Referensi