Winter & Crum, p. 161. Winter, Douglas & Crum, Adam (2002). An Insider's Guide to Collecting Type I Double Eagles. Irvine, CA: Newport Communications Group, Inc. ASINB000WCRDKG.
Winter & Crum, pp. 18–19. Winter, Douglas & Crum, Adam (2002). An Insider's Guide to Collecting Type I Double Eagles. Irvine, CA: Newport Communications Group, Inc. ASINB000WCRDKG.