Porter, Michael E., author
Free Press, 1980
Buku Teks
Porter, Michael E., author
The Free Press , 1985
Buku Teks
Gray, Edmund R., author
Macmillan, 1990
Buku Teks
Porter, Michael E., author
Free Press a Division of Macmillan, 2004
Buku Teks
Porter, Michael E., author
The Free Press , 1990
Buku Teks