Superspace formulations of the (super)twistor string
  The superspace formulation of the worldvolume action of twistor string models is considered. It is shown that for the Berkovits-Siegel closed twistor string such a formulation is provided by a N=4 twistor-like action of the tensionless superstring. A similar inverse twistor transform of the open twistor string model (Berkovits model) results in a dynamical system containing two copies of the D=4, N=4 superspace coordinate functions, one left-moving and one right-moving, that are glued by the boundary conditions.   We also discuss possible candidates for a tensionful superstring action leading to the twistor string in the tensionless limit as well as multidimensional counterparts of twistor strings in the framework of both `standard' superspace and superspace enlarged by tensorial coordinates (tensorial superspaces), which constitute a natural framework for massless higher spin theories. 
Igor A. Bandos, Jose A. de Azcarraga and Cesar Miquel-Espanya