@workingPaper{BauerBiundoDenglerKoehlerPaul_1992, title={PHI : a logic-based tool for intelligent help systems}, author={Bauer, Mathias and Biundo, Susanne and Dengler, Dietmar and Koehler, Jana and Paul, Gabriele}, doi={http://dx.doi.org/10.22028/D291-24865}, year={1992} }