Joyce David Joyce David Joyce Joyce Prof. D. Joyce webpage plane symmetry groups 17 wallpaper groups « The 17 plane symmetry groups » 17 wallpaper groups http://www.clarku.edu/~djoyce/wallpaper/seventeen.html http://www.clarku.edu/~djoyce/wallpaper/seventeen.html http://www.clarku.edu/~djoyce/wallpaper/seventeen.html 17 wallpaper groups Seventeen wallpaper patterns (site 2)