This is a rather incomplete implementation of work done by Gudrun Putze-Meier
<gudrun.pm@t-online.de>. I have to confess that I never read her original
paper. So all credit belongs to her, all bugs are mine. I tried to get some
insight from an implementation of two students of mine. They remain anonymous
because their work was the wost piece of code I ever saw. My code behaves
mostly as their implementation did except it is about 75 times faster.
