[Freeswitch-dev] Development Info

Hello, I'm new to freewitch and I would like to develop an endpoint. Is there any book / tutorial / other info about development in Freeswitch? I couldn't find any info on the internet, but there are relevant courses, which take place once a year, so there must be some presntations / other documents. I'll be glad if someone can tell me where to download / buy the books or documents. Thanks, Emil.