On equivalence of summability methods
Using δ-quasi-monotone and any almost increasing sequences we prove a theorem on summability factors of infinite series, which generalizes a theorem of Mazhar [7] on summability factors.
Estimates of the strong means of Marcinkiewicz type with the Cesaro means of negative order in one of the variables instead of square partial sums are obtained by characteristics constructed on the basis of moduli of continuity.