"United States Census, 1900," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:M367-C31 : Frank Henn, Precincts 1-6, Astor, Altoona, Acron, Crows Bluff, Cassia, Seneca, Lake, Florida, United States; citing sheet 5A, family 81, NARA microfilm publication T623 (Washington, D.C.: National Archives and Records Administration, n.d.); FHL microfilm 1,240,172.
[United States World War I Draft Registration Cards, 1917-1918," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:K35C-XJK : Ernest Otto Henn, 1917-1918; citing Jacksonville City no 1, Florida, United States, NARA microfilm publication M1509 (Washington D.C.: National Archives and Records Administration, n.d.); FHL microfilm 1,556,859.]
"Florida Death Index, 1877-1998," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:VVJT-YN5 : Ernest Otto Henn, 1943; from "Florida Death Index, 1877-1998," index, Ancestry (www.ancestry.com : 2004); citing vol. 1055, certificate number 15757, Florida Department of Health, Office of Vital Records, Jacksonville.