  We consider a system of semi-linear partial differential equations with
measurable coefficients and a nonlinear Neumann boundary condition. We then
construct a sequence of penalized partial differential equations which
converges to a solution of our initial problem. The solution we construct is in
the L p --viscosity sense, since the coefficients can be not continuous. The
method we use is based on backward stochastic differential equations and their
S-tightness. The present work is motivated by the fact that many partial
differential equations arising in physics have discontinuous coefficients.
