Publications de l'Institut Mathematique, cilt.112, sa.126, ss.143-150, 2022 (ESCI)
In 1964 Šalát presented a notion of asymptotic density of single dimensional subseries. Using this notion he presented a series of theorems similar to the following. If dn be a decreasing sequence such that (Formula Presented) and let the subseries (Formula Presented) of the series (Formula Presented) be convergent, then (Formula Presented). Following Šalát’s patten, we present a notion of double subseries and a natural variation of Šalát’s theorem.