Duff, R. W. (2010). Retirement breakthrough: The safe, secure way to guaranteed income you can't outlive-- in any economy. Greenleaf Book Group Press.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रDuff, Richard W. Retirement Breakthrough: The Safe, Secure Way to Guaranteed Income You Can't Outlive-- in Any Economy. Austin, Texas: Greenleaf Book Group Press, 2010.
एमएलए (8वां संस्करण) प्रशस्ति पत्रDuff, Richard W. Retirement Breakthrough: The Safe, Secure Way to Guaranteed Income You Can't Outlive-- in Any Economy. Greenleaf Book Group Press, 2010.
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