anchor.diff:        COMMON /ABC0/ A3,A5,A7,B3,B5,B7,C3,C5,C7
         COMMON /KVARS0/ K1,K2,K3
         COMMON /ZVARS0/ U3,V3,W3
  +      COMMON /PRODUCTS/ xx,xy,yy,dd,xd,xc,xq,yq,dq,pq
         COMMON /TAG/ thru
  -      
  -      xx = x*x
  -      xy = x*y
  -      xd = x*d
  -      cx = c*x
  -      pq = p*q
   
         if (thru.eq.0) then
             fz(1,1) =  CA1*(cd+3.0d0*d*q/R2)/R3  + CA2*3.0d0*xx*U3/R5
  
positive.code:       COMMON /ABC0/   A3,A5,A7,B3,B5,B7,C3,C5,C7
        COMMON /JVARS0/ J1,J2,J3,J4
        COMMON /KVARS0/ K1,K2,K3
        COMMON /TAG/    thru
        
        xy = x*y
        xc = x*c
        xq = x*q
        yq = y*q
        dq = d*q
        pq = p*q
  
  C----
  C When calculating terms from real source (thru = 0), include all
  
negative.code:       COMMON /KVARS0/ K1,K2,K3
        COMMON /YVARS0/ U2,V2,W2
        COMMON /ZVARS0/ U3,V3,W3
        COMMON /PRODUCTS/ xx,xy,yy,dd,xd,xc,xq,yq,dq,pq
        
        xx = x*x
        xy = x*y
        yy = y*y
        dd = d*d
        xd = x*d
        xc = x*c
  
  C R = total distance between source and station
        R  = dsqrt(xx+yy+dd)
  