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Short helpfile for action PLANE
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The input trajectory can be in any of the following formats: 

                  ATOMS - the three or four atoms whose plane we are computing. For 
                          more information on how to specify lists of atoms see \ref Group 

The following options are available

  NUMERICAL_DERIVATIVES - ( default=off ) calculate the derivatives for these 
                          quantities numerically 
                  NOPBC - ( default=off ) ignore the periodic boundary conditions 
                          when calculating distances 

