There were certain localized slave societies in East Africa, out of Zanzibar by the eighteenth and nineteenth century.

8至19世纪的东非除了桑吉巴之外,都存在小范围的奴隶社会

耶鲁公开课 - 美国内战与重建课程节选

All right, so one thing that I first want to point outabout MO theory that is a big difference from Lewis structures, is that in MO theory valence electrons are de-localized over the entire molecule.

好了，对于MO理论低一点要指出的,是它和Lewis有着很大的区别，在MO理论里,价电子在整个分子里是去局域化的。

麻省理工公开课 - 化学原理课程节选