@article{etna_vol17_pp93-101,
  author  = {Mar{\'i}a G. Armentano and Ricardo G. Dur\'an},
  title   = {Asymptotic lower bounds for eigenvalues by nonconforming finite element methods},
  journal = {Electron. Trans. Numer. Anal.},
  volume  = {17},
  year    = {2004},
  pages   = {93--101},
}