enrich documentations of example page

doc/examples.dox

@@ -71,6 +71,21 @@
  * As a result, the output VTK files document all
  * the steps of the mesh manipulation process.
  *
+ *  * Example: periodic
+ *
+ *    Create a connectivity structure for a periodic unit square.
+ * The left and right faces are identified, and bottom and top opposite.
+ *
+ *    Usage:
+ *    > `p4est_simple periodic 5`
+ *    or with MPI:
+ *    > `mpirun -np 4 p4est_simple periodic 5`
+ *
+ *    * No. of trees: 1
+ *    * Maximum refinement level: chosen on the command line as 5
+ *
+ *  \image html periodic_balanced_lv5.png
+ *
  *  * Example: circle
  *
  *    Create a connectivity structure for an donut-like circle.
@@ -100,18 +115,37 @@
  *    > `mpirun -np 7 p4est_simple drop 5`
  *
  *    * No. of trees: 5
- *    * Maximum no. of level: chosen on the command line as 5
- *
+ *    * Maximum refinement level: chosen on the command line as 5
  *  \image html drop_balanced_lv5.png
+ *
+ *  * Example: moebius
+ *
+ *    Create a connectivity structure for a five-tree moebius band.
+ *
+ *    Usage:
+ *    > `p4est_simple moebius 5`
+ *    or with MPI:
+ *    > `mpirun -np 4 p4est_simple moebius 5`
+ *
+ *    * No. of trees: 5
+ *    * Maximum refinement level: chosen on the command line as 5
+ *
+ *  \image html moebius_balanced_lv5.png
  */
 
 /** \example steps/p4est_step1.c
+ *  This software refines a basic domain using given image data.
+ * As a result, the resulting VTK file showcases the message 'Hello
+ * World' through the mesh.
  *
  * Usage:
  *    > `p4est_step1`
  */
 
 /** \example simple/simple2.c
+ * This application generates, refines, and adjusts an internally set
+ * geometry. The resulting VTK files visually present each stage of the
+ * mesh modification procedure.
  *
  * Usage:
  *    > `p4est_simple <configuration> <level>`