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  • 1 Department of Mathematics, Istanbul Tiçaret University, Istanbul, Turkey
  • 2 Department of Mathematics, Indiana University, Bloomington, IN 47405-7106, USA
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We obtain necessary conditions for a doubly triangular matrix A to have the property that a double series ΣΣ λmnbmn is summable |A|k whenever the series ΣΣbmn is bounded |A|k.