Parkinson, C. Northcote (Cyril Northcote), 1909-1993, author
Federal Publications, 1992
Buku Teks
Etzel, Michael J., author
McGraw-Hill, 2004
Buku Teks
Phillips, Charles F., author
Boston , Houghton Mifflin
Buku Teks
by Roger A. Kerin ... [and others]
McGraw-Hill, 2002
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Berkowitz, Eric N., author
Times Mirror/Mosby College, 1986
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