Lasher, William R.
Western College Publishing , 2000
Buku Teks SO
Faguet, Dmitri
John Wiley & Sons, 2003
Buku Teks SO
by Joseph T. Straub
Gemini Books, 2000
Buku Referensi
Foulke, Roy Anderson, 1896-
McGraw-Hill, 1968
Buku Teks
Foulke, Roy Anderson, 1896-
Tata McGraw-Hill, 1957
Buku Teks