@Article{ 
  MonSoc21,
  author = { Monti, Roberto and Socionovo, Alessandro },
  title = { Non-minimality of spirals in sub-Riemannian manifolds },
  journal = { Calculus of Variations and Partial Differential Equations },
  year = { 2021 },
  doi = { https://doi.org/10.1007/s00526-021-02077-4 },
  volume = { 60 },
  number = { 218 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/6885/ },
  note = { cvgmt preprint}
}