"United States Census, 1940," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/K7VX-J2J : accessed 24 January 2015), Dirk Algra in household of Roy Algra, Wells Town, Monroe, Wisconsin, United States; citing enumeration district (ED) 41-41, sheet 3A, family 42, NARA digital publication T627 (Washington, D.C.: National Archives and Records Administration, 2012), roll 4505.