Langdon-Dahm, M. (1986). Trade secrets: 25 proven success tools for working, dealing ... Learning development systems.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रLangdon-Dahm, Martha. Trade Secrets: 25 Proven Success Tools for Working, Dealing ... Dayton: Learning development systems, 1986.
एमएलए (9वां संस्करण) प्रशस्ति पत्रLangdon-Dahm, Martha. Trade Secrets: 25 Proven Success Tools for Working, Dealing ... Learning development systems, 1986.
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