@article{EJDE_2011__2011__a88,
     author = {Wen,  Guo-Chun},
     title = {Oblique derivative problems for second-order hyperbolic equations with degenerate curve},
     journal = {Electronic journal of differential equations},
     year = {2011},
     volume = {2011},
     zbl = {1213.35291},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2011__2011__a88/}
}