Snow, Edgar, author
Random House, 1958
Buku Teks
Stavrianos, Leften Stavros, author
Prentice-Hall, c1988
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