On the existence and multiplicity of extensions in dialectical
  argumentation
  In the present paper, the existence and multiplicity problems of extensions
are addressed. The focus is on extension of the stable type. The main result of
the paper is an elegant characterization of the existence and multiplicity of
extensions in terms of the notion of dialectical justification, a close cousin
of the notion of admissibility. The characterization is given in the context of
the particular logic for dialectical argumentation DEFLOG. The results are of
direct relevance for several well-established models of defeasible reasoning
(like default logic, logic programming and argumentation frameworks), since
elsewhere dialectical argumentation has been shown to have close formal
connections with these models.
