@InProceedings{HH03b,
  author = 	 {Ralf Hartmann and Paul Houston},
  title = 	 {Goal-Oriented A Posteriori Error Estimation for Multiple Target Functionals},
  booktitle = 	 {Hyperbolic problems: theory, numerics, applications},
  pages =	 {579-588},
  year = 	 2003,
  editor =	 {Thomas Y. Hou and Eitan Tadmor},
  publisher =	 {Springer},
}