anchor.diff:  
   *    ************************************
   *    *					*
  -*    *	    gen_BEEF_unrestricted	*
  +*    *	    gen_BEEF_BW_unrestricted	*
   *    *					*
   *    ************************************
   *
  
positive.code: 
  *    ************************************
  *    *                                  *
  *    *        gen_BEEF_xc_restricted    *
  *    *                                  *
  *    ************************************
  
  
negative.code: *             fn(n2ft3d)  : d(n*xce)/dn
  *             fdn(n2ft3d) : d(n*xce/d|grad n|
  *
        subroutine gen_BEEF_BW_restricted(n2ft3d,rho_in,agr_in,
       >                                x_parameter,c_parameter,
       >                                xce,fn,fdn)
  *
  