              The real-space (linear) correlation coefficient RSCC, as\
               described by Jones et al., evaluated over all atoms in the\
               nucleic acid monomer.\
\
                      sum|p~obs~ - <p~obs~>| * sum|p~calc~ - <p~calc~>|\
               RSCC = -------------------------------------------------\
                            [ sum|p~obs~  - <p~obs~> |^2^\
                            * sum|p~calc~ - <p~calc~>|^2^ ]^1/2^\
\
               p~obs~  = the density in an "experimental" map\
               p~calc~ = the density in a "calculated" map\
\
               sum is taken over the specified grid points\
\
               The details of how these maps were calculated should be described\
               in _struct_mon_details.RSCC. < > indicates an average and the\
               sums are taken over all map grid  points near the relevant atoms.\
               The radius for including grid points in the calculation should\
               also be given in _struct_mon_details.RSCC.\
\
               Ref: Jones, T. A., Zou, J. Y., Cowan, S. W. \& Kjeldgaard, M.\
                    (1991). Acta Cryst. A47, 110-119.