https://oz.fandom.com/wiki/The_Wizard_of_Oz_Wiki
Though it is fan curated and not a scholarly source, the Oz Wiki is a reliable online encyclopedia dedicated to the expansive universe of The Wizard of Oz which no Ozian should be without! It spans the original works of L. Frank Baum, the subsequent Oz series, adaptations, and related media, even including niche and obscure projects. It is exceptionally handy in tracing the evolution of Oz lore and Oz’s undeniable spell it has cast on pop culture. You can even check out the evolution of the slippers themselves in "magical items!"
You can browse the Oz wiki via: