anchor.diff:  c
   c...  subroutine arguments
   c
  -      integer ipstrs,numsn,numnp,nstep,lgdefp,kto
  +      integer ipstrs,numsn,numnp,nstep,lgdefp,ierr
         integer idslp(numsn),ipslp(npdim,numsn)
         double precision x(nsd,numnp),d(ndof,numnp),skew(nskdim,numnp)
  +      character errstrng*(*)
   c
   c...  intrinsic functions
   c
  
positive.code:       if(numsn.eq.ifour) nd=ifour
        if(numsn.eq.ithree) nd=ithree
        if(numsn.lt.ithree) then
          write(kto,*) 'Not enough points to define a plane in skcomp!'
          stop
        end if
        ncvm=ithree
        ldtmp=lgdefp
  
negative.code: c
  c
        subroutine skcomp(x,d,skew,idslp,ipslp,ipstrs,numsn,numnp,nstep,
       & lgdefp,ierr,errstrng)
  c
  c...  subroutine to compute skew angles for a given load vector and
  c     fault orientation
  