I know you said about this in your notes, but I've found a quote bu Del Toro saying:
But, the one book that I would say was a huge influence on making the movie is a book called The Sands of Fairy Tales which is a recent catalog of all the primordial streaks of storytelling in fairy tale lore.
BUT - I also found a page saying that 'Sands' is a typo, and the book he meant was 'Science'.
The Science of Fairy Tales
The whole book seems to be available here:
We can have a look through it, find the parts which relate to the film and then maybe put some quotes alongside some screenshots from the film, which could work.