Sources-On Fairy Stories

On Fairy-Stories-orginally an Andrew Lang lecture by JRR Tolkien it was incorporated as an essay into a small book titled Tree and Leaf. Versions of the essay and articles relating to it can be found online and Tree and Leaf is readily available as a book. Here are a few examples (not comprehensive) of where it can be sourced, I have tried to link directly to the relevant web page on the site where possible:

Online Book Sellers-Amazon , Harper Collins , Abe Books

Library-for example North Yorkshire Libraries

Book shops-(you may have to order), you could try finding an independent local bookshop in your area