Pugh, Richard Crawford
St.paul Minn, 1993
Buku Teks
John E. Noyes
St.paul Minn, 1997
Buku Teks
Dickinson, Edwin D.
The Foundation Press, Inc, 1950
Buku Teks
Beamish, Paul W., 1953-
Irwin, 1997
Buku Teks
Litvak, Isaiah A.
McGraw-Hill Ryerson, 1984
Buku Teks