              The mean phasing power P for reflections in this derivative\
               in this shell.\
\
                          sum|Fh~calc~^2^|\
               P = (----------------------------)^1/2^\
                    sum|Fph~obs~ - Fph~calc~|^2^  \
\
               Fph~obs~  = the observed structure factor amplitude of the\
                           derivative\
               Fph~calc~ = the calculated structure factor amplitude of the\
                           derivative\
               Fh~calc~  = the calculated structure factor amplitude from the\
                           heavy atom model\
\
               sum is taken over the specified reflections