@article{etna_vol22_pp114-121,
  author  = {Chen Greif and Dominik Sch\"otzau},
  title   = {Preconditioners for saddle point linear systems with highly singular (1,1) blocks},
  journal = {Electron. Trans. Numer. Anal.},
  volume  = {22},
  year    = {2006},
  pages   = {114--121},
}