Sources |
- [S1788] https://www.findagrave.com, Headstone, Duff, Robert E., (https://www.findagrave.com/memorial/24196240/robert-earl-duff) (Reliability: 2).
- [S178] Ancestry.com, 1940 United States Federal Census, Clay City, Clay County, Illinois, (District 13-3) (Village), image 15, page 7b, (https://www.ancestry.com/interactive/2442/M-T0627-00769-00053?backurl=http%3a%2f%2fsearch.ancestry.com%2fsearch%2fdb.asp) (Reliability: 3).
- [S198] Ancestry.com, 1930 United States Federal Census, Clay City, Illinois, (District 0003) (Village), image 02, page 1b, (https://www.ancestry.com/interactive/6224/4584337_00604?backurl=https%3a%2f%2fsearch.ancestry.com%2fsearch%2fdb.aspx%3fd) (Reliability: 3).
- [S1672] Ancestry.com, 1920 United States Federal Census, Clay City, Clay County, Illinois, Enumeration District 3, Page 13A, (http://search.ancestry.com/content/viewer.aspx?dbid=6061&iid=4300174_00632&noredir=true&sid=&gskw=) (Reliability: 2).
- [S200] Ancestry.com, 1930 Federal Census, Clay City, Illinois, District 3 (Village), page 1b, (http://search.ancestry.com/Browse/BookView.aspx?dbid=6224&iid=4584337_00605&sid=&gskw=), none. (Reliability: 2).
- [S1789] Obituary, Duff, Robert E. Jr., none. (Reliability: 2).
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