ADDED   mttroot/mtt/bin/trans/p/mtt_implicit.p
Index: mttroot/mtt/bin/trans/p/mtt_implicit.p
==================================================================
--- /dev/null
+++ mttroot/mtt/bin/trans/p/mtt_implicit.p
@@ -0,0 +1,19 @@
+PROCEDURE mtt_implicit(VAR xnew,x,dx : StateVector;
+		       VAR AA	     : StateMatrix;
+		       VAR AAx	     : StateVector;
+			   dt	     : REAL;
+			   Nx	     : INTEGER);
+
+VAR
+   i : INTEGER;
+   BB  : StateVector;
+
+(*$I $MTTPATH/trans/p/mtt_ludcmp.p *)
+(*$I $MTTPATH/trans/p/mtt_lubksb.p *)
+(*$I $MTTPATH/trans/p/mtt_solve_lud.p *)
+
+BEGIN{mtt_implicit}
+   FOR i := 1 TO  Nx DO {BB is (1-A*dt)*x +dx*dt}
+      BB[i] := AAx[i] + dt*dx[i];
+   mtt_solve_lud(xnew,AA,BB,Nx); {Solve AAx=BB}
+END;{mtt_implicit}