الفهرس 
SUMMARY
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Abstract
The objective of this dissertation is to study the stability, boundedness, asymptotic behaviour and periodicity of solutions for some scalar and vector non-linear ordinary differential equations of the fourth and fifth-order.
We present some concepts and methods of the qualitative theory of ordinary differential equations, which are needed for the study of stability and boundedness of the solutions of certain non-linear differential equations . also we introduce some theorems concerning the exis tevce of periodic solutions of non-autonomous differential systems.