@article{Allgayer-etal89-xtra,
  author	= {Allgayer, J{\"u}rgen and Harbusch, Karin and Kobsa, Alfred and Reddig, Carola and Reithinger, Norbert and Schmauks, Dagmar},
  year		= {1989},
  title		= {XTRA: a Natural-Language Access System to Expert Systems},
  journal	= {International Journal of Man-Machine Communication},
  volume	= {31},
  number	= {2},
  pages		= {161--195}
}