checkCIF procedure

PLAT931

 Check the proposed Twin Law. The entry in () represents the proposed rotation
 axis in reciprocal space and the one in [] the corresponding rotation in
 direct space. The relevant Twin Matrix can be found in the '.ckf' file.  
 Note: This test is based on F(calc)**2 values calculated with the data in the
 CIF. This ALERT can be ignored when twinning has been addressed in the
 refinement (As indicated by the Absence of ALERT_930). Please make sure that
 twinning is mentioned in the write-up of the structure report or paper.