That rule is explained in detail on slides 45-46 of the temporal logic chapter. There are the following important equivalences that allow us to remove conjunctions of temporal operations by a temporal operator which is sometimes required for a translation to CTL:

- [a1 SU b1] & [a2 SU b2] = [(a1 & a2) SU (b1 & [a2 SU b2] | b2 & [a1 SU b1])]
- [a1 SU b1] & [a2 WU b2] = [(a1 & a2) SU (b1 & [a2 WU b2] | b2 & [a1 SU b1])]
- [a1 WU b1] & [a2 WU b2] = [(a1 & a2) WU (b1 & [a2 WU b2] | b2 & [a1 WU b1])]

Slides 47-49 consider conjunctions with all other temporal operators which are reduced to the above three basic laws.