@article{NUMA_1989__54_3_133341,
     author = {Harry Yserentant},
     title = {Preconditioning {Indefinite} {Discretization} {Matrices.}},
     journal = {Numerische Mathematik},
     pages = {719--734},
     publisher = {mathdoc},
     volume = {54},
     number = {3},
     year = {1989},
     zbl = {0663.65042},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1989__54_3_133341/}
}