Also not available-
Motherwell, Minstrelsy (not 20th C.)
Dunson and Raim, 1973, Anthology of American Folk Music

The Berea Collection contains "correspondence, song texts, and folklore narrative material collected from students by folklore scholar E. C. Perrow, while he was teaching at the University of Louisville diring the early teens of the 1900s. Narrative subject areas include anecdotes, games, riddles, rhymes and superstitions."
http://www.berea.edu/hutchinslibrary/specialcollections/saa67.asp#e_c_perrow
(Series XII, Boxes 9-10).
The Roberts, Thomas, Combs, Montell, Halpert, newspaper and other collections in the 'D. K. Wilgus Folklore Collections' also in the Hutchins Library, many not published.