ダグラス郡区 (アイオワ州クレイ郡)
↑ Gillespie, Samuel (1909). History of Clay County, Iowa: From Its Earliest Settlement to 1909. S. J. Clarke Publishing Company. pp. 60. https://books.google.com/books?id=oYQUAAAAYAAJ&pg=PA60#v=onepage&q&f=false