Ensemble-style Self-training on Citation Classification Cailing Dong author Ulrich Schäfer author 2011-11 text Proceedings of 5th International Joint Conference on Natural Language Processing Haifeng Wang editor David Yarowsky editor Asian Federation of Natural Language Processing Chiang Mai, Thailand conference publication dong-schafer-2011-ensemble https://aclanthology.org/I11-1070/ 2011-11 623 631