Additionally, as long as the various minima are met (which will vary according to when and where a type was certified) it can be any LARGER number the OEM felt a good idea. Usually desire for short landing distances dictates as low a Vref as can be managed, but sometimes other factors come into play.
Vsr0 is 'reference' stall speed i.e. stall speed determined according to the 1'g' stall rules. Take away the 'r' for 'reference' and you get Vs0, the old-fashioned 'Vmin' stall speed. You should never see both the 1.23Vsr0 and the 1.3Vs0 rules at the same time, because you only determine stall speed the one way or the other, and then use the relevant speed factors for the method you used.