Liouville theory can be obtained from the S L 2 ( R ) Wess–Zumino–Witten model by a quantum Drinfeld–Sokolov reduction. Moreover, correlation functions of the H 3 + model (the Euclidean version of the S L 2 ( R ) WZW model) can be expressed in terms of correlation functions of Liouville theory. This is also true of correlation functions of the 2d black hole S L 2 / U 1 coset model. Moreover, there exist theories that continuously interpolate between Liouville theory and the H 3 + model.