Subject: What's the correct form of Heisenberg's uncertaint

All over the internet and more recently, on 2 books co-authored by the same
physicist (Robert Resnick; _Quantum Physics_ and _Fundamentals of Physics
Extended_) I've seen the standard form of the Heisenberg principle be
expressed in the 2 following ways:

delta_x * delta_p >= h-bar
delta_x * delta_p >= h-bar/2

Is there a correct one or both are right, one being simply stricter than
the other in some situation?

In any case, what is the reason for this disparity?

Thanks,

Flavio

Re: What's the correct form of Heisenberg's uncertaint