@article{etna_vol6_pp133-152,
  author  = {R. Hiptmair},
  title   = {Multigrid method for $H({\rm div})$ in three dimensions},
  journal = {Electron. Trans. Numer. Anal.},
  volume  = {6},
  year    = {1997},
  pages   = {133--152},
}