APA (7th ed.) Zitazioa
Porter, M. E. (1980). Competitive strategy. The Free Press.
Chicago Style (17th ed.) Zitazioa
Porter, Michael E. Competitive Strategy. London: The Free Press, 1980.
MLA (9th ed.) Zitazioa
Porter, Michael E. Competitive Strategy. The Free Press, 1980.
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