Fractional Superstrings with Critical Spacetime Dimensions Four and Six:   A Status Report
  Fractional superstrings are non-trivial generalizations of ordinary superstrings and heterotic strings, and have critical spacetime dimensions which are less than ten by virtue of a worldsheet fractional supersymmetry relating worldsheet bosons to worldsheet parafermions. In this paper, I provide a short non-technical survey of the fundamental issues involved in these recently-proposed theories. After introducing the basic ideas which underlie these new string theories, I review their early successes and outline some related outstanding questions.   ( Talk given at the Internal Workshop on String Theory,   Quantum Gravity, and the Unification of the Fundamental   Interactions, held in Rome, Italy, 21-26 September 1992. ) 
Keith R. Dienes (McGill Univ.)