@Article{ dixgotmar95, author = {J\"{u}rgen Dix and Georg Gottlob and Viktor Marek}, title = {Reducing Disjunctive to Non-Disjunctive Semantics by Shift-Operations}, journal = {Fundamenta Informaticae}, year = {1996}, volume = {XXVIII(1/2)}, pages = {87--100} }