@article{yh-apapdcb,
  author    = {Eitan Yaffe and
               Dan Halperin},
  title     = {Approximating the Pathway Axis and the Persistence Diagrams
               for a Collection of Balls in 3-Space},
  journal   = {Discrete {\&} Computational Geometry},
  volume    = {44},
  number    = {3},
  year      = {2010},
  pages     = {660-685}
}