@article{IM2_2003_67_2_a1,
     author = {V. A. Klyachin},
     title = {Zero mean curvature surfaces of mixed type in {Minkowski} space},
     journal = {Izvestiya. Mathematics },
     pages = {209--224},
     publisher = {mathdoc},
     volume = {67},
     number = {2},
     year = {2003},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2003_67_2_a1/}
}