Vertex Operators of Open String States in the Intersecting D-brane World
  Starting with a new bosonization scheme for the \beta\gamma CFT of the super-conformal ghosts, vertex operators are constructed for massless open string states in the intersecting D-brane world. These vertex operators satisfy all requirements for a consistent RNS formulation of superstring theories, so GSO projections can be properly taken. 
Huan-Xiong Yang, Mingxing Luo, Wei-Shui Xu (Zhejiang Univ.)