In [3] it was shown that
non-hyperbolic systems of partial differential equations may sometimes be altered
by partial prolongations so they become hyperbolic. This paper solves two
problems conceming this process for normal systems with two independent
variables. First, if hyperbolicity is obtainable, it can be obtained after a
bounded number of steps, the bound depending only on the algebraic structure
of the given system and easily calculated. Second, an explicit procedure is
described whereby any system which is absolutely equivalent to a hyperbolic
system can be changed into a hyperbolic system. In addition much of the
underlying algebraic structure of such systems and their partial prolongations is
analyzed.
