1. R.P. Agarwal, Difference Equations and Inequalities: Theory, Methods and Applications, New York, 1992
2. On Gronwall–Bellman–Bihari-type integral inequalities in several variables with retardation;Akinyele;J. Math. Anal. Appl.,1984
3. On Chaplygin’s problem;Azbelev;Ukraïn. Mat. Zh.,1958
4. Theory of Solution Stability of Differential Equations;Bellman,1954
5. A generalization of lemma of Bellman and its application to uniqueness problems of differential equations;Bihari;Acta Math. Acad. Scient. Hung.,1956