@ARTICLE{XieYu:Median,
  author =       {G. Xie and T. P.-Y. Yu},
  title =        {Smoothness Analysis of Nonlinear Subdivision Schemes of Homogeneous and Affine Invariant Type},
  journal =      {Constructive Approximation},
  year =         {2005},
  volume =       {22},
  number =       {2},
  pages =        {219-254},
}