@InProceedings{lee-sturgeon-luo:2016:P16-1,
  author    = {Lee, John  and  Sturgeon, Donald  and  Luo, Mengqi},
  title     = {A CALL System for Learning Preposition Usage},
  booktitle = {Proceedings of the 54th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)},
  month     = {August},
  year      = {2016},
  address   = {Berlin, Germany},
  publisher = {Association for Computational Linguistics},
  pages     = {984--993},
  url       = {http://www.aclweb.org/anthology/P16-1093}
}