Overall estimated standard uncertainties of positional
               parameters based on Maximum likelihood residual.
               Overall ESU gives an idea about uncertainties in the position
               of averagely defined atoms (atoms with B-values equal to
               average B-value)
                 3                         N_a
  (sigma_X)2  = -----------------------------------------------------
                 8 pi2 sumi {(1/Sigma - (E_o)2 (1-m2)(SUM_AS)s2}
               SUM_AS         = (sigma_A)2/Sigma2)
               N_a            = number of atoms
               Sigma          = (sigma_{E;exp})2 + epsilon (1-{sigma_A)2)
               E_o            = normalized structure factors
               sigma_{E;exp}  = experimental uncertainties of normalized
                                structure factors
               sigma_A        = <cos 2 pi s delta_x> SQRT(Sigma_P/Sigma_N)
                                estimated using maximum likelihood
               Sigma_P        = sum_{atoms in model} f2
               Sigma_N        = sum_{atoms in crystal} f2
               f              = is formfactor of atoms
               delta_x        = expected error
               m              = is figure of merit of phases of reflection
                                included in summation delta_x expected error
               s              = reciprocal space vector
               epsilon        = multiplicity of diffracting plane
               summation is over all reflections included in refinement
               Reference for sigma_A estimation:
               "Refinement of Macromolecular Structures by the
               Maximum-Likelihood Method:" G.N. Murshudov, A.A.Vagin and
               E.J.Dodson,(1997)  Acta Crystallogr. D53, 240-255
               Reference for ESU_ML estimation:
               Simplified error estimation a la Cruickshank in macromolecular
               crystallograpy  Murshudov G.N. & Dodson E.J.  in the "CCP4
               Newsletter on protein crystallography" Number 33 ed. M.Winn