http://www.sciencedirect.com/science/article/pii/S1631068315002286
http://www.sciencedirect.com/science/article/pii/S1631068315002304
http://www.sciencedirect.com/science/article/pii/S1631068315001165
http://www.sciencedirect.com/science/article/pii/S1631068315002110
http://www.sciencedirect.com/science/article/pii/S1631068315002237