@Misc{ 
  IveMaz12,
  author = { Iversen, Mette and Mazzoleni, Dario },
  title = { Minimising convex combinations of low eigenvalues },
  journal = { ESAIM:COCV },
  year = { 2014 },
  doi = { http://dx.doi.org/10.1051/cocv/2013070 },
  volume = { 20 },
  number = { 02 },
  pages = { 442-459 },
  URL = { http://cvgmt.sns.it/paper/1871/ },
  note = { cvgmt preprint}
}