@article{MM2_1979__29_154667,
     author = {Claudio Citrini},
     title = {Discontinous {Solutions} of a {Nonlinear} {Hyperbolic} {Equation} with {Unilateral} {Constraints.}},
     journal = {Manuscripta mathematica},
     pages = {323--352},
     publisher = {mathdoc},
     volume = {29},
     year = {1979},
     zbl = {0419.35061},
     url = {http://geodesic.mathdoc.fr/item/MM2_1979__29_154667/}
}