@techreport{EndrissEtAlTR2004, author = {Ulle Endriss and Paolo Mancarella and Fariba Sadri and Giacomo Terreni and Francesca Toni}, title = {The CIFF Proof Procedure: Definition and Soundness Results}, institution = {Department of Computing, Imperial College London}, number = {2004/2}, month = {May}, year = {2004} }