  We first define the functions which ensure the transformation of momentum and
energy of a tardyon, the transformation of the wave vector and the frequency of
the associated wave. Having done this, we show that they ensure the
relativistic invariance of the quotient between momentum and wave vector and
between energy and frequency if the product between particle velocity u and
phase velocity w is a relativistic invariant (uw=c^2), a condition which is a
natural combination of special relativity theory and quantum mechanics.
