anchor.diff:        REAL*8 K1,K2,K3
         REAL*8 U2,V2,W2
         REAL*8 U3,V3,W3
  +      REAL*8 xx,xy,yy,dd,xd,xc,xq,yq,dq,pq
         INTEGER thru
   
         COMMON /SOURCE/ sd,cd,s2d,c2d,cdcd,sdsd,cdsd
  
positive.code: 
  C-------------------
  
        SUBROUTINE rectzder(fz,ksi,eta,q,z)
  C----
  C Components of z-derivatives of displacement from finite source
  C----
  
negative.code:       RETURN
        END
  
  C - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -C
  
        SUBROUTINE disp1(f,ksi,eta,q,z)
  C----
  C Components of displacement from finite source
  C----
  