I would tremendously apreciate if anyone could please shed some light on a step in The uncertainty principle, in which I have gotten stuck.

In the link provided:

HOW DID THEY GO FROM Eq. (4.93) to (4.94) [Page #51] ... I can't seem to find how this happened? Thanks.

http://farside.ph.utexas.edu/teaching/qmech/qmech.pdf