Hello,everyone. I'm looking for some good references in moduli stack and stable reduction, so I ask here for some advice. 

I knew the famous paper of Deligne-Mumford, but this paper is hard for me now, I will very happy if someone could tell me some suggestions for reading Deligne-Mumford, or give me some good references about moduli-stack and stable reduction of curves or abelian varieties.

THANK YOU VERY MUCH!