Literature Review on Rare Word Issue in Neural Machine Translation

Here is a link to a literature review I made on the topic of rare word issue and its approaches in neural machine translation. It briefly introduces neural machine translation, and then focuses on the specific present solutions to rare word issue in NMT. Feel free to make comments on it.

https://drive.google.com/open?id=0Bxp-YYmYjAazYVB1ZEFsYkhHdXc