Principles of Non-stationary Hidden Markov Model and Its Applications to Sequence Labeling Task JingHui Xiao author BingQuan Liu author XiaoLong Wang author 2005 text Second International Joint Conference on Natural Language Processing: Full Papers conference publication xiao-etal-2005-principles 10.1007/11562214_72 https://aclanthology.org/I05-1072/ 2005