1. "Leo Errthum Death Cert.," Online Database, Dubuque County Courthouse, Dubuque, IA.
2. "Peter Leo Errthum Birth Cert.," Reg. G, pp 112, 166, Dubuque County Courthhouse, Dubuque, IA.
3. "Leo P. Errthum Obituary," The Dyersville Commercial, 6 Dec 2000.
4. "1920 Census," Concord Twp., Dubuque Co., IA, T625_488, 116, 1B.
5. "1930 Census," Holy Cross Town, Concord Twp., Dubuque Co., IA, T626_653, 31-4, 1A.
6. "A Family History of the Albert and Margaret Hefel Family," Ann (Hefel) Hayes, Helen (Hefel) Deutmeyer, Barb (Errthum) Taylor, Phyllis (Deutmeyer) Errthum, typist, 10 Jul 1983.
7. "Frances Errthum Death Cert.," Reg 12, p 237, Dubuque County Courthouse.
8. "Frances Hefel Obituary," The Dyersville Commercial, 22 Oct 1980.
9. "Hefel Errthum Wedding Announcement," The Dyersville Commercial, 1 Jun 1933.
10. "1920 Census," Buena Vista Twp., Clayton Co., IA, T625_484, 61, 4B.
11. "1930 Census," Buena Vista Twp., Clayton Co., IA.
12. "Nicholas Errthum Obituary," The Dyersville Commercial, 4 Nov 1937.
13. "1900 Census," Holy Cross Town, Concord Twp., Dubuque Co., IA, 90, 11.
14. "1910 Census," Concord Twp., Dubuque Co., IA, T624_401, 108, 1A.
15. "Dina Errthum Obituary," The Dubuque Telegraph Herald, 15 Dec 1962.
16. "Errthum Crippes Wed. Cert.," Reg. 6, 157, 25, Dubuque Co. Courthouse, Dubuque, IA, Jan 18, 1899.
17. "John Crippes Death Cert.," Reg. C, 39, Dubuque Co. Courthouse, Dubuque, IA.
18. "1880 Dubuque County Biographies," Western Historical Company, Chicago, 1880.
19. "John Crippes Obituary," The Dyersville Commercial, 17 Feb 1899.
20. "Crippes Lisen Wed. Cert.," Reg. 2, 143, Dubuque Co. Courthouse, Dubuque, IA.
21. "Michel Errthum Birth Cert.," 13 May 1835, National Archives Civil War Pension Files, 739128, 510863.
22. "Michel Errthum Pension Files," 739128, 510863, National Archives.
23. "Mary Errthum Obituary," The Dyersville Commercial, 31 Jul 1914.
24. "Errthum Stronk Wed. Cert.," 16 Oct 1867, National Archives Civil War Pension Files, 739128, 510863.
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