Undecidability of Subsumption in NIKL

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\begin{bibtex} @article{DBLP:journals/ai/Patel-Schneider89,

 author    = {Peter F. Patel-Schneider},
 title     = {Undecidability of Subsumption in NIKL},
 journal   = {Artif. Intell.},
 volume    = {39},
 number    = {2},
 year      = {1989},
 pages     = {263-272},
 bibsource = {DBLP, http://dblp.uni-trier.de}

}

\end{bibtex}