@inproceedings{Prautzsch1999Degree,
  Author = {Hartmut Prautzsch and Ulrich Reif},
  Title = {Degree estimates for C<sup>k</sup>-piecewise polynomial subdivision surfaces},
  Booktitle = {},
  Year = {1999},
  Note = {Adv. in: Comp. Math., 10: 209–217, 1999}
}