One of the nice things about the web is that mistakes are easy to correct. If you notice errors or have other suggestions about these two web pages, please let me know by e-mail (akc@umich.edu). If I agree, then the changes will be happily (although perhaps not immmediately) made.

The one suggestion that I probably will not consider at present is that I label everything in all the pictures. My current thinking is that the pictures should remain unlabeled and that the accompanying verbal descriptions should allow serious readers to identify and understand the picture contents. I may relent on this some time in the future, but that is my current opinion.

A. K. Christensen