@article{MZ_1977__154_172507,
     author = {Graham H. Williams},
     title = {Lipschitz {Continuous} {Solutions} for {Nonlinear} {Obstacle} {Problems.}},
     journal = {Mathematische Zeitschrift},
     pages = {51--66},
     publisher = {mathdoc},
     volume = {154},
     year = {1977},
     zbl = {0351.35028},
     url = {http://geodesic.mathdoc.fr/item/MZ_1977__154_172507/}
}