Symbolic Math as Computer Science

Is there much in the way of academic computer scientific literature on the
mechanisms underlying symbolic computing? I don't (believe I) mean _Modern
Computer Algebra_ by von zur Gathen and Gerhard. I'm really thinking in
terms of implementation along the lines of compiler theory, and formal
language theory.

My limited experience with such systems is pretty much exclusively with
Mathematica. Does anybody happen to know of literature that reveals how
Mathematica works at the fundamental level?
--
Nil conscire sibi
.