E print: http://ssrn.com/abstract=2777657
E print http://arxiv.org/abs/1609.02395
E print: http://arxiv.org/abs/1609.04620
E print https://arxiv.org/abs/1702.03838
E print https://arxiv.org/abs/1702.08029
E print https://arxiv.org/abs/1704.02638
E print https://arxiv.org/abs/1706.04163
E print https://arxiv.org/abs/1707.01457