Learning to Identify Educational Materials Samer Hassan author Rada Mihalcea author 2009-09 text Proceedings of the International Conference RANLP-2009 Galia Angelova editor Ruslan Mitkov editor Association for Computational Linguistics Borovets, Bulgaria conference publication hassan-mihalcea-2009-learning https://aclanthology.org/R09-1024/ 2009-09 123 127