Artikel Jurnal
Anderson, John D., author
McGraw-Hill, 1999
Buku Teks
Fielding, John P., author
Cambridge University Press, 1999
Buku Teks
Kuchemann, Dietrich, 1911-1976, author
Pergamon Press, 1985
Buku Teks
Comrie, Bernard, 1947-, author
Cambridge University Press, 1976
Buku Teks SO