Anti-de Sitter Quotients: When Are They Black Holes?
  We point out that the BTZ black holes, and their relatives, can be defined in a cleaner way than they originally were. The covering space can be taken to be anti-de Sitter space, period, while scri splits up into components due to Misner singularities. Our definition permits us to choose between two conflicting claims concerning BTZ black holes in 3+1 dimensions. 
Stefan Aminneborg, Ingemar Bengtsson