As your posting is over a year old, you might have already found the following information.I am not related, although with a connection for the Magers family to Edmonson county, Kentucky, I wouldn't be surprised to find some kind of distant connection somewhere to either my family or my wife's family.
Death certificate information:
Oscar (William) Dertinger, born 1891 in Illinois, son of Levi Dertinger born in Pennsylvania, unnamed mother born in Illinois.Farmhand with his residence in Sciota, (McDonough county) Illinois, died in (Limestone township) Peoria county, Illinois on 27 November 1922.Buried in Good Hope cemetery, Good Hope, McDonough County, Illinois.State death certificate #0720462.
Levi Thomas Dertinger, born 28 June 1855 in Pennsylvania, son of Frederick Dertinger born Germany and unnamed mother born in Germany.Husband of Anna "Majors".Died Swan Township, Warren County, Illinois on 1 August 1931, buried 3 August 1931 in Good Hope Cemetery, Good Hope, McDonough county, Illinois.State death certificate #0940160.
Anna Dertingir (sic), born 19 April 1861 in St. Augustine, (Knox county), Illinois, daughter of "Elyie Majors" and unnamed Patterson.Housewife, residence Swan Creek, Warren County, Illinois.Wife of "Lewis Dertinger".Died 30 January 1940 in Swan Township, Warren County, Illinois, buried 1 February 1940 in Good Hope, McDonough County, Illinois.State death certificate #0000033.
Death certificate information was compiled from two sources.First was the "Illinois Statewide Death Index, 1916-1950", produced by State of Illinois employees from original death certificates.The second source is "Illinois Deaths and Stillbirths, 1916-1947", produced by volunteer transcribers from LDS microfilms, on the FamilySearch.org website:
All three are listed on the Find A Grave website, posted in March of this year, with photos of their headstones.Here is a link to Levi's memorial, which has links to Anna and son Oscar:
I don't know if they would have had obits in the Monmouth newspaper, but they might have had in other area newspapers, including Roseville or Macomb.The Warren county or McDonough county genealogy societies might have them, or you could try the Abraham Lincoln Presidential Library; they have just about every Illinois newspaper that is available on microfilm.They're $1 each for Illinois residents, or 4 for $10 for non-Illinois residents.Turn around time has been about a month: