References
  
  [BR08]   Barakat,   M.   and   Robertz,   D.,  homalg  project  (2003-2008),
  ((http://wwwb.math.rwth-aachen.de/homalg)).
  
  [Gör08a]  Görtzen,  S., Simplicial Cohomology of Orbifolds, Master's thesis,
  RWTH Aachen University (2008), ((in preparation)).
  
  [Gör08b]     Görtzen,     S.,    Wallpaper    Group    Cohomology    (2008),
  ((http://wwwb.math.rwth-aachen.de/goertzen/)).
  
  [MP99]  Moerdijk,  I.  and Pronk, D. A., Simplicial cohomology of orbifolds,
  Indag. Math. (N.S.), 10, 2 (1999), 269--293.