Hi,

This book, A Study of the Miracle of Our Lady Told by Chaucer's Prioress, by Carleton Brown is the most comprehensive on the Legend. It can be viewed on google books, here:
https://books.google.com/books?id=yAdEAAAAYAAJ&printsec=frontcover&dq=A+Study+of+the+Miracle+of+Our+Lady+Told+by+Chaucer%27s+Pri

Richie