@InCollection{ dixfurnie98, author = {J\"{u}rgen Dix and Ulrich Furbach and Ilkka Niemel\"{a}}, title = {Nonmonotonic {R}easoning: {T}owards {E}fficient {C}alculi and {I}mplementations}, booktitle = {Handbook of Automated Reasoning, Volume 2, Chapter 18}, publisher = {Elsevier-Science-Press}, year = {2001}, pages = {1121--1234}, editor = {Andrei Voronkov and Alan Robinson} }