From de Camp to C. C. Klingan regarding REH's middle name, April 19, 1977

Typed Letter SIGNED “L. Sprague de Camp” dated “19 April 77” on de Camp’s own letterhead with content on Robert E. Howard. Written to C.C. Clingan (addressed to Chet), who was the editor of the sci-fi fanzine The Diversifier (1974-1979) where de Camp’s writing appeared in 1976 and 1978. The opening paragraph thanks Clingan for the copy of “REH” (perhaps a reference to the bio-bibliography of Howard, The Last Celt, published the previous year). He then goes on to discuss the variations of spelling of Howard’s middle name—“The name appears as ‘Ervine’ on the birth and death certificates of REH and his mother, but as ‘Ervin’ in all of REH’s writings about his family and on the gravestone at Brownwood,” and concludes, “In any case, to make a big fuss about the matter, as Everts (a.k.a. Kirsch) did, tells more about Everts than about the Howard family.” The middle portion of the letter speaks of the spelling of de Camp within his own family. 
 
Dampstaining to lower corner, toning and smudge, edgewear, two chips and light wrinkle to upper right edge not affecting text.

Source:

Information is found at Crow Hop Rare Books. The original letter is for sale.