* <li> @p UCD (unstructured cell data) format: this format is used
* for grid input as well as data output. If there are data vectors in
* the input file, they are ignored, as we are only interested in the
- * grid in this class. The exact description of the format can be
- * found in the AVS Explorer manual (see http://www.avs.com).
- * The @p UCD format can be read by the read_ucd() function.
+ * grid in this class. The UCD format requires the vertices to be
+ * in following ordering: in 2d
+ * @verbatim
+ * 3-----2
+ * | |
+ * | |
+ * | |
+ * 0-----1
+ * @endverbatim
+ * and in 3d
+ * @verbatim
+ * 7-------6 7-------6
+ * /| | / /|
+ * / | | / / |
+ * / | | / / |
+ * 3 | | 3-------2 |
+ * | 4-------5 | | 5
+ * | / / | | /
+ * | / / | | /
+ * |/ / | |/
+ * 0-------1 0-------1
+ * @endverbatim
+ * Note, that this ordering is different from the deal.II numbering
+ * scheme, see the Triangulation class. The exact description of the
+ * UCD format can be found in the AVS Explorer manual (see
+ * http://www.avs.com). The @p UCD format can be read by the
+ * read_ucd() function.
*
* <li> <tt>DB mesh</tt> format: this format is used by the @p BAMG mesh
* generator (see