@InProceedings{	  dix91cumulativity,
  author	= {J\"{u}rgen Dix},
  title		= {{C}umulativity and {R}ationality in {S}emantics of
		  {N}ormal {L}ogic {P}rograms},
  booktitle	= {Proceedings of the first Workshop on Nonmonotonic and
		  Inductive Logic 1990 in Karlsruhe},
  year		= {1991},
  editor	= {J. Dix and K. P. Jantke and P. H. Schmitt},
  pages		= {13--37},
  series	= {LNCS 543},
  publisher	= {Springer},
  address	= {Berlin},
  month		= {October}
}