17 Plane Crystallographic groups

• Crystallography and Cohomology of Groups
  
  • Howard Hiller
  • The American Mathematical Monthly, Vol. 93, No. 10 (Dec., 1986), pp. 765-779
• The Orbifold Notation for Two-Dimensional Groups
  
  • John H. Conway and Daniel H. Huson
    
  • Structural Chemistry, Volume 13, Numbers 3-4, August 2002 , pp. 247-257(11)
    
• • Doris Schattschneider
  • The American Mathematical Monthly, Vol. 85, No. 6 (Jun. - Jul., 1978), pp. 439-450The Plane Symmetry Groups: Their Recognition and Notation