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uboat.net
Helgason, Guðmundur. "HMS Polyanthus (K 47)". German U-boats of WWII - uboat.net. Retrieved 12 January 2025.
web.archive.org
Millie Arnet; Michelle Frisque; Beth Kean; Elizabeth T. Mahoney. "Resource Guide – Ernest Howard Shepard". The Elizabeth Nesbitt Room Illustrators Project. University of Pittsburgh ULS. Archived from the original on 3 February 2013. Retrieved 23 May 2008.