A Well-Posed Free Boundary Value Problem for a Hyperbolic Equation with Dirichlet Boundary Conditions.

John V. Matthews David G. Schaeffer A Well-Posed Free Boundary Value Problem for a Hyperbolic Equation with Dirichlet Boundary Conditions. 256-271 2004 36 SIAM J. Math. Analysis 1 http://dx.doi.org/10.1137/S0036141002408708 db/journals/siamma/siamma36.html#MatthewsS04