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  [[20XBBN+78[120X]  [16XBrown,  H.,  Bülow,  R.,  Neubüser,  J.,  Wondratschek,  H.  and  Zassenhaus,  H.[116X, [17XCrystallographic Groups of
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  Dordrecht (1995).
  
  [[20XNPW81[120X] [16XNeubüser, J., Plesken, W. and Wondratschek, H.[116X, [17XAn emendatory discursion on defining crystal systems[117X, [18XMatch[118X, [19X10[119X
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