@incollection{TielenMollerVuik2020a,
  title         = {A direct projection to low-order level for p-multigrid methods in Isogeometric Analysis},
  author        = {Roel Tielen and Matthias M{\"o}ller and Kees Vuik},
  year          = {2020},
  booktitle     = {Proceedings of ENUMATH 2019, the 13th European Conferences on Numerical Mathematics and Advanced Applications},
  publisher     = {Springer-Verlag},
  editors       = {Vermolen et al.}
}