Johnson, Anne (1914). Notable women of St. Louis, 1914. St. Louis, Woodward. p. 20. Retrieved 17 August 2017. This article incorporates text from this source, which is in the public domain.
"Gerhard Sisters". The Library of Congress. Retrieved 3 October 2017. This source incorporate text from the Library of Congress. Text created by employees of the Library of Congress in the scope of their employment are U.S. Government works is not subjected to copyright in the United States (17 U.S.C. ยง105). Unless otherwise indicated, the Library of Congress has no objection to the international use and reuse of Library U.S. Government works on loc.gov. These works are also available for worldwide use and reuse under CC0 1.0 Universal. Prepared by: Beverly W. Brannan, Curator of Photography, Prints & Photographs Division, 2011. Last revised: May 2011.
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Information from Royal Photographic Society membership records and reports in the Photographic Journal. Accessed 2 September 2021.