An extensive look at the sources and development of the legend of Robin Hood. Up to the Romantic Era. The Child ballads are in the chapter "Later Tradition."
Having hit on the first mention, in Piers Plowman, where Sloth says he knows rhymes of Robin Hood, it goes on to the next century, where we have actual tales. It covers the five known medieval ballads -- A Gest of Robyn Hode, Robin Hood and the Monk, Robin Hood and the Potter, Robin Hood his Death, and Robin Hood and Guy of Gisbourne -- and what we can learn. For instance, though they make mention of Sherwood and Nottingham, they make more of Barnsdale, the geographical references to Barnsdale are more detailed, and Barnsdale was a notorious haunt of robbers. Gest is obviously a compendium of tales, you can see the joins where they are not neatly soldered together, and we have, of course, no way of knowing what was left out.
It discusses the history of the claims to historicity for Robin but doesn't think any of them really arguable. Oddly enough, the Victorian folklorist, who, in the grand sweeping inaccurate style in which they so often indulged, tried to turn Robin Hood into a wood spirit on evidence inadequate to hang a dog, went out to debunk the claimed historicity -- because it would of course undermine the mythic origin -- and in the process introduced much more rigor into the claims. His discussion of the obvious sources make it even clear. Such outlaws as Hereward the Wake, Fulk fitz Waren and Eustace the Monk have pre-dating tales that the early Robin Hood ones were clearly based on, and such ones as Adam Bell were part of the same outlaw tradition of tales. Though the tale in the Geste about paying the knight's mortgage is unique to Robin, despite having a motif that appears elsewhere. No robbing from the rich to give to the poor, actually. A lot of violence. The use of pseudonyms by outlaws -- often Robin, but not with Hood. And Friar Tuck. The first appearance of that name as an outlaw listed it as a novelty, so he may be the first.
It also goes into the physical setting and the region of England claimed, and into the audiences that listened and what sort of information we can glean about its original era by the social terms used. The use in the May Games and how Marian and quite possibly a friar joined the legend from there. Marian often had a boyfriend named Robin, and once there was a fad for Robin Hood games at May festivities, it was probably inevitable. The spread of the tale, with Shakespeare citing it in As You Like It, and the introduction of Allan-a-Dale. The Elizabethean tale where he married Clorinda, the Queen of Shepherdess -- she didn't manage to displace Marian, obviously. The Child Ballads and Sir Walter Scott with his introduction of the Saxon/Norman thing. The new uses of it, with Robin as a dispossessed nobleman, and Robin as a social rebel.
It ends before it even gets to Howard Pyle, but there's a lot of Robin Hood history in the earlier ages.