1. Asymptotic behavior of solutions of certain problems for ordinary nonlinear differential equations with a small parameter multiplying the highest derivatives;Vasil'eva;Usp. Mat. Nauk,1963
2. Solutions of nonlinear differential equations with a small parameter by asymptotic series;Wasow;Ann. Math.,1959
3. Asymptotic behaviour of the solutions of systems of differential equations with a small parameter in the highest derivatives;Pontryagin;Izv. Akad. Nauk SSSR, Ser. Mat.,1959
4. On systems of non-linear ordinary differential equations containing a parameter;Iwano,1961
5. On systems of non-linear ordinary differential equations containing a parameter. II;Iwano,1962