"United States Census, 1920," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MWT1-KL3 : accessed 9 August 2015), William Groothius in household of Sabena Groothius, Stoneham, Chippewa, Minnesota, United States; citing sheet 3A, family 37, NARA microfilm publication T625 (Washington D.C.: National Archives and Records Administration, n.d.); FHL microfilm 1,820,826.