@Article{ 
  DeLFri17,
  author = { De Luca, Lucia and Friesecke, Gero },
  title = { Crystallization in two dimensions and a discrete Gauss-Bonnet theorem },
  journal = { J. Nonlinear Sci. },
  year = { 2017 },
  doi = { 10.1007/s00332-017-9401-6 },
  volume = { 28 },
  number = { 1 },
  pages = { 69--90 },
  URL = { http://cvgmt.sns.it/paper/3321/ },
  note = { cvgmt preprint}
}