  In this article, a new proof is given of the description of the center of
quadratic Sklyanin algebras of global dimension three and four and the center
of cubic Sklyanin algebras of global dimension three. The representation theory
of the Heisenberg groups $H_2$, $H_3$ and $H_4$ will play an important role. In
addition a new proof is given of Van den Bergh's result regarding
noncommutative quadrics.
