@proceedings {citation222, title = {The infinite PCFG using Hierarchical Dirichlet Processes}, journal = {Empirical Methods in Natural Language Processing}, year = {2007}, month = {2007}, url = {http://www.cs.berkeley.edu/~jordan/papers/hdppcfg-emnlp2007.pdf}, author = {Percy Liang and Slav Petrov and Michael I. Jordan and Dan Klein} }