Five years later, this question is still valid.

[Here][1] (pages 16 and 17) you can find a great explanation, including an Algorithm.


  [1]: https://ecirtam.net/autoblogs/autoblogs/zythomblogspotfr_2530d81ebaf87a9d212b9c420da28b772b9e5cb4/media/445d3ada.bms-basic-NLP_120609.pdf