Can you give references?

1. 位移电流不承受电荷力的作用可能导致动量不守恒. (references?)
2. 很多物理学家避之惟恐不及，这朵乌云从19世纪一直飘到21世纪.(references?)

To my knowledge, 光在介质中特别是在透明介质中的动量仍然是个谜. See: Weilong She, Jianhui Yu, and Raohui Feng, "Observation of a Push Force on the End Face of a Nanometer Silica Filament Exerted by Outgoing Light," Phys. Rev. Lett. 101, 243601 (2008).

Thanks a lot.