checkCIF procedure

PLAT127

 The reported Hall-symbol is not identical to the one internally tabulated
 for the space-group as derived from the explicitly supplied symmetry
 operations. As an example, the Hall symbols '-P 2yn' and '-P 2yabc' both 
 correspond with space-group 'P21/n'. Alternatively, no Hall-symbol could be
 derived by PLATON for the explicit set of symmetry operations. This may be
 the case when an unusual origin is chosen. 
 Refer to: S.R.Hall, Space-group Notation with an Explicit Origin;  
           Acta Cryst. (1981), A37, 517-525.
       or: http://cci.lbl.gov/sginfo/hall_symbols.html