Find a Grave, database and images (https://www.findagrave.com/memorial/73074335/harold-gustaf-sellin : accessed 01 March 2022), memorial page for Harold Gustaf Sellin Sr. (unknown–1961), Find a Grave Memorial ID 73074335, citing Forest Lawn Memorial Park, Omaha, Douglas County, Nebraska, USA ; Maintained by Marvin & Samme Templin (contributor 426307) .
"Iowa, Delayed Birth Records, 1850-1939," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:Q246-CW76 : accessed 2 March 2022), Harold Gustav Sellin, 13 Dec 1894, Creston, Union, Iowa, United States; citing reference ID 156395, State Historical Society of Iowa, Des Moines; FamilySearch digital folder 101713784.
"United States Census, 1910," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MG9N-BM4 : accessed 2 March 2022), Harold G Sellin in household of John W Sellin, Union, Union, Iowa, United States; citing enumeration district (ED) ED 159, sheet 7A, family 126, NARA microfilm publication T624 (Washington D.C.: National Archives and Records Administration, 1982), roll 425; FHL microfilm 1,374,438.
"United States Census, 1930," database with images, FamilySearch (https://www.familysearch.org/ark:/61903/1:1:XQK8-23K : accessed 2 March 2022), Harold G Sellin, Omaha, Douglas, Nebraska, United States; citing enumeration district (ED) ED 84, sheet 32A, line 16, family 288, NARA microfilm publication T626 (Washington D.C.: National Archives and Records Administration, 2002), roll 1276; FHL microfilm 2,341,011.
"United States Census, 1940," database with images, FamilySearch (https://www.familysearch.org/ark:/61903/1:1:K999-NTB : 6 January 2021), Harold Sellin, Omaha, Douglas, Nebraska, United States; citing enumeration district (ED) 94-33, sheet 7A, line 18, family 161, 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 2269.
"Iowa State Census, 1915," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:QK4Y-72CM : 2 March 2022), Harold Sellin, 1915; citing Afton, Union, Iowa, United States, card no. , Iowa State Historical Department, Des Moines; FHL microfilm 1,462,843.