@article{ainsworthkay2000,
  title = "Approximation theory for the hp-version finite element method and application to the non-linear Laplacian",
  author = "M. Ainsworth and D. Kay",
  year = "2000",
  journal = "Appl. Num. Math.",
  pages = "329--344",
  volume = "34",
  doi = "10.1016/S0168-9274(99)00040-9",
}