Need Asterisk architecture information

Hi all,

I am co-authoring a book on VoIP for leading publisher. Asterisk has a great contribution to open source movement in the VoIP domain. I want to know about the core architecture of the Asterisk.

Can anyone please send me some information regarding the same.

downloads.oreilly.com/books/9780596510480.pdf
Then you can install asterisk, and create docs.