@article{EJDE_1999__1999__a74,
     author = {Aberra,  Dawit},
     title = {On a generalized reflection law for functions satisfying the {Helmholtz} equation},
     journal = {Electronic journal of differential equations},
     year = {1999},
     volume = {1999},
     zbl = {0921.31001},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_1999__1999__a74/}
}