The Massless Spectrum of Covariant Superstrings
  We obtain the correct cohomology at any ghost number for the open and closed covariant superstring, quantized by an approach which we recently developed. We define physical states by the usual condition of BRST invariance and a new condition involving a new current which is related to a grading of the underlying affine Lie algebra. 
P.A. Grassi (SUNY, Stony Brook), G. Policastro (Pisa, Scuola Normale   Superiore), and P. van Nieuwenhuizen (SUNY, Stony Brook)