The first one will be above and below the bond axis is where we'll see the electron density, and the second will be perpendicular to that, so it will be a density in front of and behind the bond axis.

第一个是在键轴之上和之下,我们可以看到电子密度，另外一个垂直于它，所以在键轴之前和之后有电子密度。

麻省理工公开课 - 化学原理课程节选

Then, when we open up the front, we see the author's note to the second edition, and this was something O'Connor added to the novel in 1962.

然后当我们打开书的前几页，会看到作者对第二版的注解，这是奥康纳在1962年加上去的。

耶鲁公开课 - 1945年后的美国小说课程节选