"United States Census, 1870," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MHC8-PZW : accessed 29 July 2015), Jacob Witkop in household of Fraark Witkop, Michigan, United States; citing p. 16, family 126, NARA microfilm publication M593 (Washington D.C.: National Archives and Records Administration, n.d.); FHL microfilm 552,196.