Boxer, Robert J., author
McGraw-Hill, 1998
Buku Referensi
Denniston, Katherine J., author
Wm. C. Brown, 1993
Buku Teks
Weeks, Daniel P., author
Saunders College, 1995
Buku Teks
Neckers, Douglas C.
John Wiley & Sons, 1977
Buku Teks
Wilbraham, Anthony C., author
ITB Press, 1992
Buku Teks