@Article{BR01a,
  author = 	 {Wolfgang Bangerth and Rolf Rannacher},
  title = 	 {Adaptive Finite Element Techniques for the Acoustic Wave Equation},
  journal = 	 {J. Comput. Acoustics},
  year = 	 2001,
  volume =	 9,
  number =	 2,
  pages =	 {575--591}
}