1. (1) Kojima, On the convergence-abscissa of general Dirichlet's series, Tôhoku Math. Journal, 6 (1914), 134-139.
2. Lindh, Sur un nouveau théorème dans la théorie des séries de Dirichlet, Comptes Rendus, 160 (1915), 271-273.
3. (2) Hardy and L'ttlewood, Tauberian theorems concerning power series and Dirichlet's series whose coefficients are positive, Proc. London Math. Soc., Ser. 2, 13 (1914), 174-191.
4. (3) This theorem is also due to Hardy and Littlewood. See Hardy and Littlewood, Some theorems concerning Dirichlet's series, Mess. of Math., 43 (1914), 134-147. See also Boh-Cramer, Enzyklopädie, IIc, 8, 732.
5. (4) In which [y] stands for the integral part of y.