Ward, Dederick C.
Scarecrow Press, 1981
Buku Referensi
Harbaugh, John W., author
WMC Brown, 1974
Buku Teks
edited by J.F. White
Prentice-Hall, 1962
Buku Teks
Wilson, Gilbert, author
George Allen, 1982
Buku Teks
Butler, B.C.M., author
Longman Scientific & Technical , 1988
Buku Teks