Stationary planets

1
While reading Horary Astrology by Anthony Lewis, I noticed that he mention in two different occasions that, before having a direct motion, stationary planets are very powerful.

Can somebody tell me where can I find more information about it?

Thank you in advance.

2
I don`t know any specific references but the energy of stationary planets are intense and powerful not only when they are about go direct but also before turning Rx.