"United States Census, 1900," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/M92P-N7K : accessed 26 February 2015), Gertie De Young in household of Albert De Young, Black Oak Township, Mahaska, Iowa, United States; citing sheet 1B, family 13, NARA microfilm publication T623 (Washington, D.C.: National Archives and Records Administration, n.d.); FHL microfilm 1,240,446.