Drennan, D., & Pennington, S. (1999). 12 ladders to world class performance: How your organization can compete with the best in the world. Kogan Page.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रDrennan, David, और Stewart Pennington. 12 Ladders to World Class Performance: How Your Organization Can Compete with the Best in the World. London: Kogan Page, 1999.
एमएलए (9वां संस्करण) प्रशस्ति पत्रDrennan, David, और Stewart Pennington. 12 Ladders to World Class Performance: How Your Organization Can Compete with the Best in the World. Kogan Page, 1999.
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