"United States Census, 1930," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:XH1J-QZH : accessed 12 March 2021), Young Cho Choy in household of Doo Woon Choy, Honolulu, Honolulu, Hawaii, United States; citing enumeration district (ED) ED 43, sheet 19A, line 8, family 323, NARA microfilm publication T626 (Washington D.C.: National Archives and Records Administration, 2002), roll 2634; FHL microfilm 2,342,368.
"United States Census, 1940," database with images, FamilySearch (https://www.familysearch.org/ark:/61903/1:1:VB96-W82 : 5 January 2021), Herbert Choy in household of Doo W Choy, Representative District 4, Honolulu, Hawaii Territory, United States; citing enumeration district (ED) 2-29, sheet 11B, line 98, family 219, 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 4584.
"United States Social Security Death Index," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:J5FH-SP1 : 11 January 2021), Herbert Y C Choy, 10 Mar 2004; citing U.S. Social Security Administration, Death Master File, database (Alexandria, Virginia: National Technical Information Service, ongoing).