text: * Orbifold signature: 
  * Coxeter notation (rectangular): [((&infin;,2),(&infin;,2))]
  * Coxeter notation (square): [4,4]
  * Lattice: rectangular
  * Point group: D
  * The group pgg contains two rotation centres of order two (180°), and glide reflections in two perpendicular directions. The centres of rotation are not located on the glide reflection axes. There are no reflections.
  ;Examples of group pgg