Ward, Richard
Prentice-Hall, 1965
Buku Teks SO
edited by R.N. Cooper
Penguin Books, 1969
Buku Teks SO
Day, Alan
British Broadcasting , 1968
Buku Teks SO
editor, Brian J. Terry
Toppan Company, 1997
Buku Referensi
Copeland, Laurence S.
Prentice-Hall, 2008
Buku Teks SO