@Article{ 
  Neg15,
  author = { Negri, Matteo },
  title = { A simple derivation and classical representations of energy variations for curved cracks },
  journal = { Appl. Math. Optim. },
  year = { 2017 },
  doi = { 10.1007/s00245-016-9328-6 },
  volume = { 75 },
  pages = { 99-116 },
  URL = { http://cvgmt.sns.it/paper/2691/ },
  note = { cvgmt preprint}
}