Heard this was a better place for my question; if this is the wrong subreddit, I apologize.

I'm doing some research on Western Slavic people for a story I'm working on; first chunk focuses on a small tribe in what is now northern Poland in the mid 6th century. I'm also hoping to include the deities Morena, Vesna, Perun and Veles.

I've done some basic research (read: I Googled and checked Wikipedia) but would like to be a little more accurate. Do you have any advice on books/websites I should check out/avoid like the plague?

Thanks in advance.