Headington, Mark R.
Jones and Bartlett Publisher, 1997
Buku Teks SO
Schildt, Herbert
McGraw-Hill, 2001
Buku Teks SO
McCracken, Daniel D.
John Wiley & Sons, 1974
Buku Referensi
Pagan, Frank G.
John Wiley & Sons, 1976
Buku Teks SO
McGettrick, Andrew D.
Cambridge Univeristy Press, 1982
Buku Teks SO