"When it is all said and done, I think it is time for a 'do over'. We need to start this budget process all over again.

VOA: standard.2009.03.24

And again, I want you to have practiced drawing these out in the form you always need to start with the sigma and then write the number of the orbital.

同样的，我希望你们,练习画这种图,你总是要从sigma开始,然后写出轨道数目。

麻省理工公开课 - 化学原理课程节选