Thanks, truth be told I have flown that way half a dozen times over the past 5 years and never called ahead after departing HKG, but flew with a captain the other day who insisted. He produced what I think (from memory) was the Jeppesen China H/L 1/2 IFR enroute chart, pointed to ball note "5" for BEKOL which in the chart margins states "contact next atc agency 3 minutes prior to crossing", without referencing specific frequencies on which to do so. Obviously we are aware of the call aheads inbound to HKG but those are more clearly annotated on the charts.