Symmetries of String Effective Action and Space-Time Geometry
  Two dimensional charged black hole solution is obtained by implementing an $O(2,2)$ transformation on the three dimensional black string solution. Two different monopole backgrounds in five dimensions are related through an $O(2,2)$ transformation. It has been shown in these examples that the particular $O(2,2)$ transformation corresponds to duality transformation. 
S. Pratik Khastgir and Jnanadeva Maharana