  In the paper "On the interpolation of integer-valued polynomials" (Journal of
Number Theory 133 (2013), pp. 4224--4232.) V. Volkov and F. Petrov consider the
problem of existence of the so-called $n$-universal sets (related to
simultaneous $p$-orderings of Bhargava) in the ring of Gaussian integers. We
extend their results to arbitrary imaginary quadratic number fields and prove
an existence theorem that provides a strong counterexample to a conjecture of
Volkov-Petrov on minimal cardinality of $n$-universal sets. Along the way, we
discover a link with Euler-Kronecker constants and prove a lower bound on
Euler-Kronecker constants which is of the same order of magnitude as the one
obtained by Ihara.
