Bridges 2011 Regular Paper

The problem of identifying how many (doubly periodic) patterns exist on the plane, which are different from the point of view of symmetry can be approached in different ways and using different mathematical tools. And the final conclusion that there are only a finite number is by no means evident a priori. Using the DVD Symmetry---the dynamical way extensively we will look at examples of stamps with different shapes and properties, which produce figures with different types of symmetry.