Abstract:
The following theorem is proved: the union of countable many closed $U_{r}$-sets ($r>2$)
for the Vilenkin–Dzhafarli system is again a $U_{r}$-set for this system.
Key words:group of $p$-adic intergers, zero-dimensional group, characters of a group, Vilenkin–Dzhafarli system, $U_r$-sets.