Sulla convergenza delle serie reali a termini non negativi

In this paper some necessary and sufficient conditions are given for convergence of a series with non-negative terms. As a particular case, one finds again the well-known ratio-test for convergence of series with positive terms; in such a connection, some observations are made of didactical interest. Finally, some relations are emphasiged concerning theorems of convergence for real series (here obtained) and fixed point theorems already known.