Self-dual solutions of 2+1 Einstein gravity with a negative cosmological   constant
  All the causally regular geometries obtained from (2+1)-anti-de Sitter space by identifications by isometries of the form $P \rightarrow (\exp \pi\xi) P$, where $\xi$ is a self-dual Killing vector of $so(2,2)$, are explicitely constructed. Their remarkable properties (Killing vectors, Killing spinors) are listed. These solutions of Einstein gravity with negative cosmological constant are also invariant under the string duality transformation applied to the angular translational symmetry $\phi \rightarrow \phi+a$ The analysis is made particularly convenient through the construction of {\em global} coordinates adapted to the identifications.} 
O. Coussaert and M. Henneaux