Boeing says Vref is equal to 1.3 Vs (for the landing flaps configuration).
Those of you adepts of D.P.Davies "Handling the big jets" will also recall his Vat definition, as "speed at threshold"...
At PanAm, we called that speed "Vth" or "vee-thresh".
Vref+5 seems to be the norm of the industry, as the target speed for landing.
Plus winds additives, as described above, not to exceed 20 knots.
And J.T. mentioned carrying Vref+10 for the 727-200. I did that too.
xxx
Happy contrails