"United States Census, 1920," database with images, FamilySearch (https://www.familysearch.org/ark:/61903/1:1:MFK3-5Q2 : accessed 25 December 2020), Peter Kohler, Milwaukee, Milwaukee, Wisconsin, United States; citing ED 245, sheet 11B, line 52, family 262, NARA microfilm publication T625 (Washington D.C.: National Archives and Records Administration, 1992), roll 2003; FHL microfilm 1,822,003.
"United States Census, 1930," database with images, FamilySearch (https://www.familysearch.org/ark:/61903/1:1:X93W-689 : accessed 25 December 2020), Peter Kohler, Menomonee Falls, Waukesha, Wisconsin, United States; citing enumeration district (ED) ED 15, sheet 8B, line 63, family 161, NARA microfilm publication T626 (Washington D.C.: National Archives and Records Administration, 2002), roll 2616; FHL microfilm 2,342,350.
"United States Census, 1940," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:K7KW-GMH : 29 July 2019), Peter Kohler, Menomonee Town, Waukesha, Wisconsin, United States; citing enumeration district (ED) 67-18, sheet 7A, line 12, family 128, Sixteenth Census of the United States, 1940, NARA digital publication T627. Records of the Bureau of the Census, 1790 - 2007, RG 29. Washington, D.C.: National Archives and Records Administration, 2012, roll 4533.