Porter, M. E. (1998). On competition. Harvard Businesss School Publishing.
Cita Chicago (17th ed.)Porter, Michael E. On Competition. Boston: Harvard Businesss School Publishing, 1998.
Cita MLA (9th ed.)Porter, Michael E. On Competition. Harvard Businesss School Publishing, 1998.
Atenció: Aquestes cites poden no estar 100% correctes.