diff --git a/gprMax/geometry_outputs.py b/gprMax/geometry_outputs.py
index b0a12e9b..65760bcc 100644
--- a/gprMax/geometry_outputs.py
+++ b/gprMax/geometry_outputs.py
@@ -24,10 +24,10 @@ import numpy as np
 from struct import pack
 
 from gprMax._version import __version__
+from gprMax.geometry_outputs_ext import define_normal_geometry
+from gprMax.geometry_outputs_ext import define_fine_geometry
 from gprMax.utilities import round_value
 
-from .geometry_outputs_ext import define_fine_geometry, define_normal_geometry
-
 
 class GeometryView(object):
     """Views of the geometry of the model."""
@@ -70,7 +70,7 @@ class GeometryView(object):
             self.vtk_yfcells = self.yf // self.dy
             self.vtk_zscells = self.zs // self.dz
             self.vtk_zfcells = self.zf // self.dz
-            self.vtk_nxcells = self.nx // self.dx 
+            self.vtk_nxcells = self.nx // self.dx
             self.vtk_nycells = self.ny // self.dy
             self.vtk_nzcells = self.nz // self.dz
             self.n_vtk_cells = self.vtk_nxcells * self.vtk_nycells * self.vtk_nzcells
@@ -136,7 +136,7 @@ class GeometryView(object):
                 f.write('<DataArray type="Int8" Name="Receivers" format="appended" offset="{}" />\n'.format(vtk_rxs_offset).encode('utf-8'))
                 f.write('</CellData>\n'.encode('utf-8'))
                 f.write('</Piece>\n</ImageData>\n<AppendedData encoding="raw">\n_'.encode('utf-8'))
-                
+
                 solid_geometry = np.zeros((self.n_vtk_cells), dtype=np.uint32)
                 srcs_pml_geometry = np.zeros((self.n_vtk_cells), dtype=np.int8)
                 rxs_geometry = np.zeros((self.n_vtk_cells), dtype=np.int8)
@@ -197,8 +197,8 @@ class GeometryView(object):
                 f.write('</CellData>\n'.encode('utf-8'))
 
                 f.write('</Piece>\n</PolyData>\n<AppendedData encoding="raw">\n_'.encode('utf-8'))
-                
-                # Coordinates of each point                
+
+                # Coordinates of each point
                 n_points = (self.nx + 1) * (self.ny + 1) * (self.nz + 1)
                 points = np.zeros((n_points, 3), dtype=np.float32)
 
diff --git a/gprMax/geometry_outputs_ext.pyx b/gprMax/geometry_outputs_ext.pyx
index c1182a81..b2fc4aaa 100644
--- a/gprMax/geometry_outputs_ext.pyx
+++ b/gprMax/geometry_outputs_ext.pyx
@@ -1,7 +1,26 @@
+# Copyright (C) 2015-2018: The University of Edinburgh
+#                 Authors: Craig Warren and Antonis Giannopoulos
+#
+# This file is part of gprMax.
+#
+# gprMax 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.
+#
+# gprMax 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 gprMax.  If not, see <http://www.gnu.org/licenses/>.
+
 cimport numpy as np
 
 from gprMax.constants cimport floattype_t
 
+
 cpdef void define_fine_geometry(
                     int nx,
                     int ny,
@@ -24,7 +43,7 @@ cpdef void define_fine_geometry(
                     np.uint32_t[:, :] z_lines,
                     np.uint32_t[:] z_materials
             ):
-    
+
     cdef Py_ssize_t i, j, k
     cdef Py_ssize_t label = 0
     cdef Py_ssize_t counter_x = 0
@@ -62,6 +81,7 @@ cpdef void define_fine_geometry(
 
                 label = label + 1
 
+
 cpdef void define_normal_geometry(
                     int xs,
                     int xf,
@@ -78,9 +98,8 @@ cpdef void define_normal_geometry(
                     np.uint32_t[:] solid_geometry,
                     np.int8_t[:] srcs_pml_geometry,
                     np.int8_t[:] rxs_geometry,
-
             ):
-    
+
     cdef Py_ssize_t i, j, k
     cdef Py_ssize_t counter = 0
 
@@ -91,6 +110,3 @@ cpdef void define_normal_geometry(
                 srcs_pml_geometry[counter] = srcs_pml[i, j, k]
                 rxs_geometry[counter] = rxs[i, j, k]
                 counter = counter + 1
-
-
-