/**
* Initialize the given triangulation with a hyper-L (in 2d or 3d)
- * consisting of exactly <tt>2^dim-1</tt> cells. It produces the hypercube
- * with the interval [<i>left,right</i>] without the hypercube made out of
- * the interval [<i>(left+right)/2,right</i>] for each coordinate. If the
- * @p colorize flag is set, the @p boundary_ids of the surfaces are
- * assigned, such that the left boundary is 0, and the others are set with
- * growing number accordingly to the counterclockwise. Colorize option works
- * only with 2-dimensional problem. This function will create the classical
- * L-shape in 2d and it will look like the following in 3d:
+ * consisting of exactly <tt>2^dim-1</tt> cells. It produces the
+ * hypercube with the interval [<i>left,right</i>] without the
+ * hypercube made out of the interval [<i>(left+right)/2,right</i>]
+ * for each coordinate. Because the domain is about the simplest one
+ * with a reentrant (i.e., non-convex) corner, solutions of many
+ * partial differential equation have singularities at this
+ * corner. That is, at the corner, the gradient or a higher
+ * derivative (depending on the boundary conditions chosen) does not
+ * remain bounded. As a consequence, this domain is often used to
+ * test convergence of schemes when the solution lacks regularity.
+ *
+ * If the @p colorize flag is set, the @p boundary_ids of the
+ * surfaces are assigned, such that the left boundary is 0, and the
+ * others are set with growing number accordingly to the
+ * counterclockwise. Colorize option works only with 2-dimensional
+ * problem. This function will create the classical L-shape in 2d
+ * and it will look like the following in 3d:
*
* @image html hyper_l.png
*
- * This function is declared to exist for triangulations of all space
+ * @note The 3d domain is also often referred to as the "Fichera corner",
+ * named after Gaetano Fichera (1922-1996) who first computed an
+ * approximation of the corner singularity exponent of the lowest
+ * eigenfunction of the domain.
+ *
+ * This function exists for triangulations of all space
* dimensions, but throws an error if called in 1d.
*
* @note The triangulation needs to be void upon calling this function.