1. Stability Theory of Differential Equations;Bellman,1953
2. Theory of Ordinary Differential Equations;Coddington,1955
3. Stability and Asymptotic Behavior of Differential Equations;Coppel,1965
4. Un teorema sul comportamento asintotico delgi integrali delle equazioni differenziali lineari omogenee;Ghizzetti;Rend. Mat. e Appl.,1949
5. Asymptotic behavior of solutions of (ry(m))(k) ± qy = 0;Hinton;J. Differential Equations,1968