Frederick, J. G. (1929). Selling by telephone. Business Bourse Publishers.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रFrederick, J. George. Selling by Telephone. New York: Business Bourse Publishers, 1929.
एमएलए (8वां संस्करण) प्रशस्ति पत्रFrederick, J. George. Selling by Telephone. Business Bourse Publishers, 1929.
चेतावनी: ये उद्धरण हमेशा 100% सटीक नहीं हो सकते हैं.