If you want to read more about dialects, I know Victor Mair (from Language Log) wrote a lot about such things in the context of Chinese (e.g., http://languagelog.ldc.upenn.edu/nll/?p=10303; http://languagelog.ldc.upenn.edu/nll/?cat=124). That's not anything specifically to do with AAVE, but more the general concept of what does and doesn't let you call something a dialect.