Beckwith Harry. (1997). Selling the invisible: A field guide to modern marketing. Warner Books / Time Warner Company.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रBeckwith Harry. Selling the Invisible: A Field Guide to Modern Marketing. NewYork ,USA: Warner Books / Time Warner Company, 1997.
एमएलए (9वां संस्करण) प्रशस्ति पत्रBeckwith Harry. Selling the Invisible: A Field Guide to Modern Marketing. Warner Books / Time Warner Company, 1997.
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