add snippet for sub/super diagonal
fix a few doc issues
diff --git a/doc/C03_TutorialGeometry.dox b/doc/C03_TutorialGeometry.dox
index b3c860d..2d3d742 100644
--- a/doc/C03_TutorialGeometry.dox
+++ b/doc/C03_TutorialGeometry.dox
@@ -10,7 +10,7 @@
   | \ref TutorialSparse "Sparse matrix"
 </div>
 
-In this tutorial chapter we will shortly introduce the many possibilities offered by the \ref GeometryModule "geometry module",
+In this tutorial chapter we will shortly introduce the many possibilities offered by the \ref Geometry_Module "geometry module",
 namely 2D and 3D rotations and affine transformations.
 
 \b Table \b of \b contents
@@ -106,7 +106,7 @@
 
 <a href="#" class="top">top</a>\section TutorialGeoCommontransformationAPI Common API across transformation types
 
-To some extent, Eigen's \ref GeometryModule "geometry module" allows you to write
+To some extent, Eigen's \ref Geometry_Module "geometry module" allows you to write
 generic algorithms working on any kind of transformation representations:
 <table class="tutorial_code">
 <tr><td>