ヴォルガ郡区 (アイオワ州クレイトン郡)
↑ Price, Realto E. (1916). History of Clayton County, Iowa: From the Earliest Historical Times Down to the Present. Robert O. Law Company. pp. 322. https://books.google.com/books?id=ZDdAAAAAYAAJ&pg=PA322#v=onepage&q&f=false