We study the propagation of hyper surfaces Sigma (t) of R-N satisfying the
equation V = h(x, Ohm (t)), where V is the normal velocity of Sigma (t) at
x, Ohm (t) is the interior of Sigma (t), and h is a given evolution law. We
prove the the distance of generalized solutions and an inclusion principle
for these generalized solutions. (C) 2001 Academic Press.