@Article{BK07,
  author = 	 {Wolfgang Bangerth and Oliver Kayser-Herold},
  title = 	 {Data Structures and Requirements for $hp$ Finite Element
                  Software},
  journal = 	 {ACM Trans. Math. Softw.},
  year = 	 2009,
  volume = 	 36,
  number = 	 1,
  pages = 	 {4/1--4/31}}