@article{EJDE_2008__2008__a27,
     author = {Kharibegashvili,  Sergo and Midodashvili,  Bidzina},
     title = {Solvability of characteristic boundary-value problems for nonlinear equations with iterated wave operator in the principal part},
     journal = {Electronic journal of differential equations},
     year = {2008},
     volume = {2008},
     zbl = {1173.35613},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2008__2008__a27/}
}