Jiantao Jiao, Haim H. Permuter, Lei Zhao, Young Han Kim, Tsachy Weissman. Universal estimation of directed information via sequential probability assignments. In Proceedings of the 2012 IEEE International Symposium on Information Theory, ISIT 2012, Cambridge, MA, USA, July 1-6, 2012. pages 523-527, IEEE, 2012. [doi]