"Iowa State Census, 1895," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/VTQK-CVM : accessed 6 February 2015), Klaus Kooiker in household of Willem Kooiker, Sioux, Iowa, United States; citing p. 17, 1895, State Historical Society, Des Moines; FHL microfilm 1,022,182.