I knew Earl Elam back in the 1970s long before he ever wrote his book, He was a prof of history at Sul Ross State College later University located in Alpine, Texas. (Where I obstained a BS). Since he admitted to me off line in a personal email that he used someone's work (with permission), but never checked any of the information for himself, I'd find it hard to use. I've spent too much time chasing false informatin in a book to bother after hearing that. Ervin has done ydna and Family Finder tests and proven his lineage. On the Elam mailing list, they all told me that they worked on clues, including Earl. Not my kind of genealogy, since I've been doing it for over 50 years.