ner_tags: O O O O O O O B-Organization I-Organization I-Organization I-Organization O B-Grant O B-Grant O O B-Person I-Person O O O O O O O O O O O O O O O O O
tokens: Acknowledgments The project was supported partially by Polish National Science Center grants DEC-2011/01/N/ST9/06000 and DEC-2012/07/B/ST9/04412. We thank Nathan Leigh for very insightful comments and suggestions which helped us to significantly improve the text of the paper.