*-- Author : S.Burke / J.V. Morris
      SUBROUTINE FKQADD(C,Q)
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*                                                                    *                                        
* Add a multiple scattering matrix to a covariance matrix            *                                        
*                                                                    *                                        
* Output is C = C + Q, lower half only, where Q(3,x) = Q(x,3) = 0    *                                        
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*