Superstring and Superstring Field Theory: a new solution using   Ultradistributions of Exponential Type
  In this paper we show that Ultradistributions of Exponential Type (UET) are appropriate for the description in a consistent way superstring and superstring field theories. A new Lagrangian for the closed superstring is given. We show that the superstring field is a linear superposition of UET of compact support, and give the notion of anti-superstring. We evaluate the propagator for the superstring field, and calculate the convolution of two of them. 
C. G. Bollini and M. C. Rocca