Selsdon, Helen (July 29, 2015). “Helen Keller: An Artificial Eye”. American Foundation for the Blind. January 9, 2022時点のオリジナルよりアーカイブ。September 23, 2021閲覧。
Selsdon, Helen (July 29, 2015). “Helen Keller: An Artificial Eye”. American Foundation for the Blind. January 9, 2022時点のオリジナルよりアーカイブ。September 23, 2021閲覧。