Books on DID

I’m writing a final paper for my psychology class on DID and while I do know a lot about it just because I’ve been fascinated by it for years, I need at least five sources for this final paper. Does anyone have any research based recommendations? The teacher is very strict about finding “valid sources” so anything by psychologists or other doctors would be greatly appreciated. I’ve already looked through the DSM and have gotten a lot of good information from it