Richards, David A.J.
Oxford University Press, 1986
Buku Teks
[date of publication not identified]
Buku Teks
Corwin, Edward S., author
United States of America, 1960
Buku Teks
Corwin, Edward S., author
Holt, Rinehart and Winston, 1966
Buku Teks
Scott, Frank R
University of Toronto Press, 1977
Buku Teks