"United States Census, 1860," index, FamilySearch (https://familysearch.org/pal:/MM9.1.1/M8L7-HKH : accessed 26 February 2015), Braer Fokkema in household of Gysbert Van Der Linden, Pella Lake Prairie Tp, Marion, Iowa, United States; from "1860 U.S. Federal Census - Population," Fold3.com; citing p. 248, household ID 1734, NARA microfilm publication M653, National Archives and Records Administration, Washington, D.C.; FHL microfilm 803,335.