checkCIF procedure

PLAT919

 This ALERT reports the number of reflections with intensities seriously
 effected by the beamstop. Reflections are counted for which theta < 3  
 Degrees and (F(obs)**2 - F(calc)**2) / sqrt(weight) < - 10.0. Those
 reflections are better removed from the final refinement since they are
 in systematic error.