@article{EJDE_1998__1998__a6,
     author = {Borsuk,  Michail and Portnyagin,  Dmitriy},
     title = {Barriers on cones for degenerate quasilinear elliptic operators},
     journal = {Electronic journal of differential equations},
     year = {1998},
     volume = {1998},
     zbl = {0893.35034},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_1998__1998__a6/}
}