This is work in progress.
To obtain documentation do the following steps:

1) Download nuweb

2) Apply the patch nuweb-latex.patch found in
this directory:
patch -i nuweb-latex.patch latex.c

3) Compile nuweb (follow program instructions) 
make nuweb 

4) Then, for example:
cd src/Engine
nuweb -v -l  -s  -d DensityMatrix.w

5) Then typeset it and rerun nuweb for references as needed:
pdflatex DensityMatrix.tex
nuweb -v -l  -s  -d DensityMatrix.w
pdflatex DensityMatrix.tex

6) and you should get the documentation in
DensityMatrix.pdf

