Southwell, E.A., author
Longmans, Green, 1947
Buku Teks
Blumenthal, Joseph C.
Harcourt Brace Jovanovich, 1972
Buku Teks
Jordan, R. R., author
Longman, 2001
Buku Teks
Roach, Peter (Peter John), author
Cambridge University Press, 1983
Buku Teks
Alexander, L.G., author
Longman, 1967
Buku Teks