@article{JMLR:v18:16-061,
  author  = {Matth{{\"a}}us Kleindessner and Ulrike von Luxburg},
  title   = {Lens Depth Function and k-Relative Neighborhood Graph: Versatile Tools for Ordinal Data Analysis},
  journal = {Journal of Machine Learning Research},
  year    = {2017},
  volume  = {18},
  number  = {58},
  pages   = {1--52},
  url     = {http://jmlr.org/papers/v18/16-061.html}
}