@article{NUMA_1993__65_4_133734,
     author = {Sze-Ping Wong},
     title = {Preconditioning {P1} nonconforming finite elements: condition numbers and singular value distributions.},
     journal = {Numerische Mathematik},
     pages = {253--272},
     publisher = {mathdoc},
     volume = {65},
     number = {4},
     year = {1993},
     zbl = {0796.65115},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1993__65_4_133734/}
}