For next time (June 17), I would suggest reading an introduction to
(lexicalised probabilistic) context-free grammars.  I found Eugene
Charniak's "Statistical Techniques for NLP" quite readable, and not
too long.  You will find it in the seminar folder or also online at:
http://www.cs.brown.edu/people/ec//papers/aimag97.ps.

Alternatively, chapter 12 from Jurafsky & Martin's "Speech and
Language Processing" covers about the same, but is a bit more verbose.
Please find it also in the folder if Charniak is too concise or
unclear.

There is a *lot* of introductory material on PCFGs available, but I
hope the above will give a good starting point, and is not too much to
digest.

Tylman Ule