@article{NUMA_1992__63_1_133693,
     author = {Xuejun Zhang},
     title = {Multilevel {Schwarz} methods.},
     journal = {Numerische Mathematik},
     pages = {521--539},
     publisher = {mathdoc},
     volume = {63},
     number = {1},
     year = {1992},
     zbl = {0796.65129},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1992__63_1_133693/}
}