Approximation problems in modular spaces of double sequences.
Aleksander Waszak (1990)
Publicacions Matemàtiques
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Let X denote the space of all real, bounded double sequences, and let Φ, φ, Γ be φ-functions. Moreover, let Ψ be an increasing, continuous function for u ≥ 0 such that Ψ(0) = 0. In this paper we consider some spaces of double sequences provided with two-modular structure given by generalized variations and the translation operator (...).