  A bibliography on the Hurwitz transformations is given. We deal here, with
some details, with two particular Hurwitz transformations, viz, the $\grq \to
\grt$ Kustaanheimo-Stiefel transformation and its $\grh \to \grc$ compact
extension. These transformations are derived in the context of
Fock-Bargmann-Schwinger calculus with special emphasis on angular momentum
theory.
