"United States Census, 1860," index, FamilySearch (https://familysearch.org/pal:/MM9.1.1/MWDZ-272 : accessed 9 January 2015), Itstje Krootsma in household of Roelff Krootsma, The Town Of Zeeland, Ottawa, Michigan, United States; from "1860 U.S. Federal Census - Population," Fold3.com; citing p. 57, household ID 439, NARA microfilm publication M653, National Archives and Records Administration, Washington, D.C.; FHL microfilm 803,557.