Notes. The values we derived from the calibrated and carefully reduced all-sky UBV observations obtained during several seasons at Hvar (station 01) were added to the appropriate magnitude differences for all differential data sets from the literature. We also tabulate the mean all-sky values derived from the final reduction of Fairborn APT and Sejong observations. For comparison, the mean V magnitude based on the transformation of the Hipparcos H_p magnitude to Johnson V after Harmanec (1998) is also tabulated for all comparison stars used. The number (No.) of individual calibrated all-sky observations on which the mean values are based is also given. Stations: 1) Hvar; 16) Fairborn T5; 61) Hipparcos; 78) Sejong.