  
  
  [1XReferences[101X
  
  [[20XEGN[120X]     [16XEick,     B.,     Gahler,    F.    and    Nickel,    W.[116X,    [17Xcryst[117X,
  {https://www.gap-system.org/Packages/cryst.html}.
  
  [[20XEll[120X] [16XEllis, G.[116X, [17XHAP[117X, {http://hamilton.nuigalway.ie/Hap/www/}.
  
  
  
  [32X
