@Article{	  dix93aclassificationtheoryi,
  author	= {J\"{u}rgen Dix},
  title		= {{A} {C}lassification-{T}heory of {S}emantics of {N}ormal
		  {L}ogic {P}rograms: {I}. {S}trong {P}roperties},
  journal	= {Fundamenta Informaticae},
  year		= {1995},
  volume	= {XXII(3)},
  pages		= {227--255}
}