CK-12 Foundation
Ck 12: Geometry: Symmetry and Tessellations Study Guide
[Free Registration/Login may be required to access all resource tools.] Provides a brief overview of the different types of symmetry and of how to tessellate a shape.
University of St. Andrews (UK)
University of St. Andrews: Wilhelm Magnus
This site, provided by the University of St. Andrews in Scotland, gives a biography of Wilhelm Magnus. Many interesting links are provided as well.