@inproceedings{lexfree2015,
    title={Lexicon-Free Conversational Speech Recognition with Neural Networks},
    author={Maas, Andrew L. and Xie, Ziang and Jurafsky, Dan and Ng, Andrew Y.},
    booktitle={Proceedings the North American Chapter of the Association for Computational Linguistics (NAACL)},
    year={2015}
}