Looking for documentation of Maxima internals.



Hello, I was wondering if there is any documentation of the Maxima 
architecture available that might help to make the source code a bit 
more accessible.  I.e. description of major data structures, internal 
functions, programming conventions, file organization etc.  Note: I am 
not looking for documentation of general CAS algorithms and Lisp.

I expect that Maxima has been used in the past as an object of study
in some computer algebra courses and there might be lecture notes and so 
on which could be helpful. Would anyone be willing to make such material 
available?