Further restructuring.

docs/source/index.rst

@@ -28,7 +28,15 @@ gprMax User Guide
 
 .. toctree::
     :maxdepth: 2
-    :caption: Example models
+    :caption: Advanced topics
+
+    python_scripting
+    openmp_mpi
+    user_libraries
+
+.. toctree::
+    :maxdepth: 2
+    :caption: Examples
 
     examples_simple_2D
     examples_antennas
@@ -43,18 +51,14 @@ gprMax User Guide
 
 .. toctree::
     :maxdepth: 2
-    :caption: Advanced topics
-
-    python_scripting
-    openmp_mpi
-    user_libraries
-
-.. toctree::
-    :maxdepth: 2
-    :caption: Appendices
+    :caption: Accuracy and performance
 
     comparisons_analytical
     comparisons_numerical
     benchmarking
+
+.. toctree::
+    :maxdepth: 2
+
     references