  This paper uses products of distributions to obtain new junction conditions
for relativistic shocks. In general, the shock is accompanied by a surface
layer, and the new conditions generalize both Taub's jump conditions for
shocks, and those of Israel and Kuchar for surface layers. In the
non-relativistic limit, the surface layer is present only when the fluid is
viscous or thermally conducting--a situation where the classical
Rankine-Hugoniot conditions do not apply. Thus, our conditions properly extend
all previous conditions, and provide complete Cauchy data needed to solve the
full Navier-Stokes equations downstream of the shock. Since the associative law
fails for our product, the residual uncertainty regarding the association of
factors must be eliminated empirically. This is equivalent to fixing the
correct initial_form_ of the equations (such as the ``conservation form'' in
the Euler case)
