problems	Contains LaTeX source for a bunch of problems
hwk/rec		Contain particular homework and recitation subdirs, e.g. hwk1

The homework subdirs link back to the particular problems in the
problems directory so the problems can live in a central location and
be reused in future quarters.

There are also non-problem directories such as `syllabus' for LaTeX
source for other course documents.  With these added to Makefile's
`SUBDIRS', the source they contain is compiled and installed in their
`INSTALL_DIR'.  Take a look at syllabus/Makefile for the particulars,
which are not too complicated.  The directory `old-source' contains
the LaTeX source from previous courses, since so much of the layout
is standardized and much of the text is boilerplate.