I don't know of any academic works off the top of my head that deal with it - it's not anything I've ever looked into academically - but I've seen a good number of primary source material (mostly video testimonies like the ones collected by Steven Spielberg's Shoah Foundation, among others) where survivors talk about it. It's not like every testimony talks about it, but if I were to guess I'd say maybe 1 in 10 survivors who spent a lot of time in the camps talk about it. That ballpark, anyway.

The one I recall most vividly was a man talking about finding a severed hand in the camp, and he and four others took turns taking one bite of flesh each until it was gone - share and share alike. His body language was such that he hardly seemed to be alive while talking about it. Flat monotone, no variation in the rhythm of his words, staring off into space. It was most startling because he was in general a very active speaker, lots of gestures and his emotions visible on his sleeve during most of the testimony.

It's the sort of thing that undoubtedly happened more often than people talked about. The few who speak of doing it are so clearly shamed and traumatized by the memory, and have such trouble talking about it, that I'm certain there are many more who can't bring themselves to do so. Much the same can be said about sexual violence during the Holocaust - nearly every female survivor testimony I've seen talks about rape, but I have never encountered a testimony where a survivor says she herself was raped. It's always a friend or a friend of a friend that gets raped.