Extending the Black Hole Uniqueness Theorems, II. Superstring Black   Holes
  We make use of an internal symmetry of a truncation of the bosonic sector of the superstring and N=4 supergravity theories to write down an analogue of Robinson's identity for the black holes of this theory. This allows us to prove the uniqueness of a restricted class of black hole solutions. In particular, we can apply the methods of the preceding paper to prove the uniqueness of a class of accelerating black holes (the Stringy Ernst solution and Stringy C-metric) which incorporate the possibility of the black hole accelerating within an electromagnetic flux tube. These solutions and their associated uniqueness may be useful in future instanton calculations. 
Clive G. Wells