Thomas, Robert Murray, 1921-
Bergin & Garvey, 2000
Buku Teks
Garson, G. David
Marcel Dekker, 2002
Buku Referensi
Madsen, David, 1929-
Jossey-Bass, 1992
Buku Teks
O`Neil, L. Peat
Writer's Digest Books, 1995
Buku Teks
Mahmoud, Shah
Betterway, 1992
Buku Referensi