1. Gronwall, T.H.: Note on the derivatives with respect to a parameter of the solutions of a system of differential equations. Ann. Math. 20, 292–296 (1919)
2. Bellman, R.: The stability of solutions of linear differential equations. Duke Math. J. 10, 643–647 (1943)
3. Pachpatte, B.G.: On some generalizations of Bellman’s lemma. J. Math. Anal. Appl. 51(1), 141–150 (1975)
4. Lakshmikantham, V., Leela, S.: Differential and Integral Inequalities, Theory and Applications. Academic Press, New York (1969)
5. EI-Owaidy, H., Ragab, A., Abdeldaim, A.: On some new integral inequalities of Gronwall–Bellman type. Appl. Math. Comput. 106, 289–303 (1999)