1. Banach, S. Théorie des opérations linéaires, Warszawa 1932.
2. Garabedian, H. L. Randels, W. C. Theorems on Riesz means, Duke Math. J.4 (1938), 529?533.
3. Hardy, G. H. The second theorem of consistency for summable series, Proc. Lond. Math. Soc. (2),15 (1916), 72?88.
4. Hardy, G. H. Orders of infinity, Cambridge 1924.
5. Hardy, G. H. Divergent series, Oxford 1949.