Harbaugh, John W.
WMC Brown, 1974
Buku Teks
Wilson, Gilbert
George Allen, 1982
Buku Teks
edited by J.F. White
Prentice-Hall, 1962
Buku Teks
Butler, B.C.M.
Longman Scientific & Technical , 1988
Buku Teks
edited by Sybil P. Parker
McGraw-Hill, 1988
Buku Referensi