Welcome to this site. I have attempted to provide some information on the group structure of wallpaper groups. For those of you who are mathematicians, I have tried to make this website accessible to as many people as possible. Some of the explanations and descriptions used may not be as rigorous as you would like. With that said, let's take a look at what I have placed here.
This site is structured so that you can skip the parts you already know about, or think you do. Specifically, one of the pages is a short tutorial on the nature of groups. This is written to be very accessible to most anyone who has had some high school algebra. There is, of course, a section on the group structures of the seventeen wallpaper groups, also known in some circles as the plane crytallography groups. Then there are sections on Frieze groups and other connections of geometry to algebra. Enjoy!
http://www2.geom.umn.edu/scienceu/geometry/articles/symmetry/
http:/www.geom.umn.edu/docs/education/institute91/
http:/www.best.com/%7exah/Wallpaper_dir/c0_WallPaper.html
This site was created on April 21, 2001 by Michael E. McCallum. For comments or suggestions contact mmccallu@bellsouth.net.