↑ Ashcroft and Mermin (1976). Solid State Physics (ấn bản 1). Holt, Reinhart, and Winston. tr. 299–302. ISBN0030839939. Truy cập ngày 2 tháng 2 năm 2018.
↑ For these negative mass electrons, crystal momentum is opposite to velocity, so forces acting on these electrons cause their velocity to change in the 'wrong' direction. As these electrons gain energy (moving towards the top of the band), they slow down.
