For a fast thumbnail sketch, to start to get a frame of reference, look him up in an encyclopedia and read the article. It may not give all the context you need, but it's a start. Ah, the memories..I took a course on Yeats my first year in college as I needed an English class, and I'd heard that he was somehow linked in with Irish folklore. Things went well, generally, but I'd naively assumed that the teacher knew as much about Irish folklore and its symbols as I did. Oops. Came the day I was blythely saying "but of course everyone knows...and I saw on their faces that it was news to the class that the white dogs with red ears were supernatural creatures....