 who discovered that the finite element method converges "exponentially fast" when
the mesh is refined using a suitable combination of h-refinements
(dividing elements into smaller ones) and p-refinements (increasing their
polynomial degree).The exponential convergence makes the method
a very attractive choice compared to most other finite element methods
which only converge with an algebraic rate.The exponential convergence
of the hp-FEM was not only predicted theoretically but also observed
by numerous independent researchers.