diff --git a/src/interpolation.F90 b/src/interpolation.F90
new file mode 100644
index 0000000..2a526be
--- /dev/null
+++ b/src/interpolation.F90
@@ -0,0 +1,93 @@
+!!*****************************************************************************
+!!
+!! module: interpolation - subroutines for different kinds of interpolation
+!!
+!! Copyright (C) 2008 Grzegorz Kowal <kowal@astro.wisc.edu>
+!!
+!!*****************************************************************************
+!!
+!!  This file is part of Godunov-AMR.
+!!
+!!  Godunov-AMR is free software; you can redistribute it and/or modify
+!!  it under the terms of the GNU General Public License as published by
+!!  the Free Software Foundation; either version 3 of the License, or
+!!  (at your option) any later version.
+!!
+!!  Godunov-AMR is distributed in the hope that it will be useful,
+!!  but WITHOUT ANY WARRANTY; without even the implied warranty of
+!!  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+!!  GNU General Public License for more details.
+!!
+!!  You should have received a copy of the GNU General Public License
+!!  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+!!
+!!*****************************************************************************
+!!
+!
+module interpolation
+
+  implicit none
+
+  contains
+!
+!===============================================================================
+!
+! reconstruct: subroutine for the reconstruction of the values at the right and
+!              left interfaces of cells from their cell centered representation
+!
+!===============================================================================
+!
+  subroutine reconstruct(n, vx, vl, vr)
+
+    implicit none
+
+! input/output arguments
+!
+    integer           , intent(in)  :: n
+    real, dimension(n), intent(in)  :: vx
+    real, dimension(n), intent(out) :: vl, vr
+
+! local variables
+!
+    integer            :: i
+    real               :: dv
+    real, dimension(n) :: ds, dvl, dvr
+!
+!------------------------------------------------------------------------------
+!
+! second order interpolation
+!
+    dvl(1) = 0.0
+    dvr(n) = 0.0
+
+    do i = 1, n-1
+      dvr(i  ) = vx(i+1) - vx(i)
+      dvl(i+1) = dvr(i)
+    enddo
+
+    do i = 1, n
+      ds (i) = dvr(i) * dvl(i)
+
+      if (ds(i) .gt. 0.0) then
+        dv  = ds(i) / (dvr(i) + dvl(i))
+
+        vl(i) = vx(i) + dv
+        vr(i) = vx(i) - dv
+      else
+        vl(i) = vx(i)
+        vr(i) = vx(i)
+      endif
+    enddo
+
+    do i = 1, n-1
+      vr(i) = vr(i+1)
+    enddo
+    vr(n) = vx(n)
+
+!-------------------------------------------------------------------------------
+!
+  end subroutine reconstruct
+
+!===============================================================================
+!
+end module
diff --git a/src/makefile b/src/makefile
index 295b5e7..d4171a9 100644
--- a/src/makefile
+++ b/src/makefile
@@ -78,10 +78,10 @@ name = godunov-amr
 
 default: $(name).x
 
-sources = blocks.F90 config.F90 driver.F90 error.F90 evolution.F90 io.F90 \
-          mesh.F90 problem.F90 scheme.F90 timer.F90
-objects = blocks.o   config.o   driver.o   error.o   evolution.o   io.o   \
-          mesh.o   problem.o   scheme.o   timer.o
+sources = blocks.F90 config.F90 driver.F90 error.F90 evolution.F90             \
+          interpolation.F90 io.F90 mesh.F90 problem.F90 scheme.F90 timer.F90
+objects = blocks.o   config.o   driver.o   error.o   evolution.o               \
+          interpolation.o   io.o   mesh.o   problem.o   scheme.o   timer.o
 files   = $(sources) makefile make.default config.in license.txt hosts
 
 $(name).x: $(objects)
@@ -103,10 +103,11 @@ config.o        : config.F90 error.o
 driver.o        : driver.F90 config.o evolution.o io.o mesh.o timer.o
 error.o         : error.F90
 evolution.o     : evolution.F90 blocks.o config.o mesh.o scheme.o
+interpolation.o : interpolation.F90
 io.o            : io.F90 blocks.o error.o
 mesh.o          : mesh.F90 blocks.o config.o error.o problem.o
 problem.o       : problem.F90 blocks.o
-scheme.o        : scheme.F90 blocks.o config.o
+scheme.o        : scheme.F90 blocks.o config.o interpolation.o
 timer.o         : timer.F90
 
 #-------------------------------------------------------------------------------
diff --git a/src/scheme.F90 b/src/scheme.F90
index a2bc846..249913c 100644
--- a/src/scheme.F90
+++ b/src/scheme.F90
@@ -188,7 +188,7 @@ module scheme
 !
   subroutine hll(m, n, uc, f)
 
-!     use interpolation, only : reconstruct, point2avg
+    use interpolation, only : reconstruct
 
     implicit none
 
@@ -205,8 +205,6 @@ module scheme
     real, dimension(m,n) :: fl, fr, fx
     real, dimension(n)   :: cl, cr
     real                 :: al, ar, ap, div
-
-    integer, parameter, dimension(6)    :: pos = (/ 1, 0, 0, 0, 1, 1 /)
 !
 !----------------------------------------------------------------------
 !
@@ -214,7 +212,7 @@ module scheme
 ! reconstruct left and right states of conserved variables
 !
     do p = 1, m
-!       call reconstruct(n,uc(p,:),ul(p,:),ur(p,:),pos(p))
+      call reconstruct(n,uc(p,:),ul(p,:),ur(p,:))
     enddo
 
 ! calculate primitive variables
@@ -230,7 +228,7 @@ module scheme
 ! reconstruct left and right states of primitive variables
 !
     do p = 1, m
-!       call reconstruct(n,qc(p,:),ql(p,:),qr(p,:),pos(p))
+      call reconstruct(n,qc(p,:),ql(p,:),qr(p,:))
     enddo
 
 ! calculate conservative variables at states