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diff --git a/math/nlfit/nliterd.x b/math/nlfit/nliterd.x
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+include <mach.h>
+include	<math/nlfit.h>
+include "nlfitdefd.h"
+
+# NLITER - Routine to compute one iteration of the fitting process
+
+procedure nliterd (nl, x, z, w, npts, nvars, ier)
+
+pointer	nl		# pointer to nl fitting structure
+double	x[ARB]		# independent variables (npts * nvars)
+double	z[ARB]		# function values (npts)
+double	w[ARB]		# weights (npts)
+int	npts		# number of points
+int	nvars		# number of independent variables
+int	ier		# error code
+
+int	i, index
+double	nlacptsd(), nlresidd()
+
+begin
+	# Do the initial accumulation.
+   	NL_OLDSQ(nl) = nlacptsd (nl, x, z, w, npts, nvars)
+
+	# Set up temporary parameter array.
+	call amovd (PARAM(NL_PARAM(nl)), TRY(NL_TRY(nl)), NL_NPARAMS(nl))
+
+	repeat {
+
+	    # Solve the matrix.
+	    call nlsolved (nl, ier)
+	    if (ier == NO_DEG_FREEDOM)
+	        return
+
+	    # Increment the parameters.
+	    do i = 1, NL_NFPARAMS(nl) {
+	        index = PLIST(NL_PLIST(nl)+i-1)
+	        TRY(NL_TRY(nl)+index-1) = TRY(NL_TRY(nl)+index-1) +
+		    DPARAM(NL_DPARAM(nl)+i-1)
+	    }
+
+	    # Reaccumulate the residuals and increment lambda.
+	    NL_SUMSQ(nl) = nlresidd (nl, x, z, w, npts, nvars)
+	    #if (NL_OLDSQ(nl) > (NL_SUMSQ(nl) + NL_TOL(nl) * NL_SUMSQ(nl))) {
+	    if (NL_OLDSQ(nl) >= NL_SUMSQ(nl)) {
+		call amovd (TRY(NL_TRY(nl)), PARAM(NL_PARAM(nl)),
+		    NL_NPARAMS(nl))
+		NL_LAMBDA(nl) = double (0.10) * NL_LAMBDA(nl)
+		break
+	    } else
+	        NL_LAMBDA(nl) = min (double(LAMBDAMAX),
+		    double (10.0) * NL_LAMBDA(nl))
+
+	} until (NL_LAMBDA(nl) <= double(0.0) ||
+	    NL_LAMBDA(nl) >= double(LAMBDAMAX))
+end