1. Theory of Ordinary Differential Equations;Coddington,1955
2. Asymptotic Behavior and Stability Problems in Ordinary Differential Equations;Cesari,1959
3. Equazioni Differenziali non Lineari;Sansone,1956
4. Sulla “equivalenza assintotica” dei sistemi di equazioni differenziali ordinarie;Conti;Ann. Mat. Pura Appl., Ser. 4,1956
5. The applications of a fixed point theorem to a variety of non-linear stability problems;Stokes,1960