--- /dev/null
+.. _connectivity_page:
+
+******************************
+Nodal connectivity of elements
+******************************
+
+The following images show order of nodes in correctly defined elements.
+
++------------------------------------------------------------------------------+
+| Edge (segment): linear and quadratic |
+| .. image:: ../images/connectivity_edge.png |
+| :align: center |
++------------------------------------------------------------------------------+
+| Triangle: linear, quadratic and bi-quadratic |
+| .. image:: ../images/connectivity_tria.png |
+| :align: center |
++------------------------------------------------------------------------------+
+| Quadrangle: linear, quadratic and bi-quadratic |
+| .. image:: ../images/connectivity_quad.png |
+| :align: center |
++------------------------------------------------------------------------------+
+| Polygon: linear and quadratic |
+| .. image:: ../images/connectivity_polygon.png |
+| :align: center |
++------------------------------------------------------------------------------+
+| Tetrahedron: linear and quadratic |
+| .. image:: ../images/connectivity_tetra.png |
+| :align: center |
++------------------------------------------------------------------------------+
+| Hexahedron: linear, quadratic and tri-quadratic |
+| .. image:: ../images/connectivity_hexa.png |
+| :align: center |
++------------------------------------------------------------------------------+
+| Pentahedron: linear and quadratic |
+| .. image:: ../images/connectivity_penta.png |
+| :align: center |
++------------------------------------------------------------------------------+
+| Pyramid: linear and quadratic |
+| .. image:: ../images/connectivity_pyramid.png |
+| :align: center |
++------------------------------------------------------------------------------+
+| Hexagonal prism |
+| .. image:: ../images/connectivity_hex_prism.png |
+| :align: center |
++------------------------------------------------------------------------------+
+| Polyhedron is defined by |
+| * a sequence of nodes defining all facets |
+| * a sequence of number of nodes per facet |
+| |
+| **Nodes**: |
+| Node1_of_Facet1, Node2_of_Facet1, ..., NodeN_of_Facet1, |
+| Node1_of_Facet2, Node2_of_Facet2, ..., NodeN_of_Facet2, |
+| Node1_of_FacetM, Node2_of_FacetM, ..., NodeN_of_FacetM |
+| |
+| **Quantity** of nodes per facet: |
+| NbNodes_in_Facet1, NbNodes_in_Facet2, ..., NbNodes_in_FacetM |
+| |
+| For example the polyhedron shown in the image below is defined by nodes |
+| [ 1,2,3, 1,4,5,2, 2,5,6,3, 3,6,4,1, 4,7,9,5, 5,9,8,6, 6,8,7,4, 7,8,9 ] |
+| and quantities [ 3, 4, 4, 4, 4, 4, 4, 3 ] |
+| |
+| .. image:: ../images/connectivity_polyhedron.png |
+| :align: center |
+| |
+| Order of nodes of a facet must assure outward direction of its normal. |
++------------------------------------------------------------------------------+
+
