Taiwanese Journal of Mathematics, cilt.8, sa.3, ss.453-465, 2004 (SCI-Expanded)
Let A and B be two summability methods. We shall use the notation λ ∈ (A, B) to denote the set of all sequences λ such that ∑a nλn is summable B, whenever ∑an is summable A. In the present paper we characterize the sets λ ∈ (|N̄,pn|, |T|k) and λ ∈ (|N̄,p n|k, |T|), where T is a lower triangular matrix with positive entries and row sums 1. As special cases we obtain summability factor theorems and inclusion theorems for pairs of weighted mean matrices.