"United States Census, 1930", database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:X7Z2-CD1 : accessed 18 January 2016), Thurman C Knapp in entry for Theodore L Knapp, 1930.
"United States Census, 1940," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:KQ5T-3MW : accessed 18 January 2016), Thurman Knapp in household of Theodore Knapp, Dolgeville, Manheim Town, Herkimer, New York, United States; citing enumeration district (ED) 22-54, sheet 2B, family 56, NARA digital publication T627 (Washington, D.C.: National Archives and Records Administration, 2012), roll 2543.