References
- Zeszyty naukowe U.J. Prace Matemat v.6 On the convergent to zero of the solutions of the second order differentiaal equations A. Lasota
- Dokl. Akad. Nauk. SSSR v.141 On the stability of solutions of second order differential equations A. J. Levin
- Atti Accad. Naz/ Lincei, Rend Serive Ⅷ, v.LXIX Note on the behaviour of solutions of a second order nonlinear difference equation B. Szmanda