2 suggestions: 1) Ask people in mechanical turk to write those sentences. Then you can ask others to verify them - you get far with few dollars 2) Include hig

2 suggestions: 1) Ask people in mechanical turk to write those sentences. Then you can ask others to verify them - you get far with few dollars 2) Include higher level features - for example bi-grams, there is more information in them Also: corpus at http://thatswhatshesaid.com/ http://thatswhatshesaid.com/ (I have no relation with this site)