1. Z. Artstein, Continuous dependence of solutions of Volterra integral equations, SIAM J. Math. Anal., 6 (1975), 446–456.
2. V. Barbu, Integro-differential equations in Hilbert spaces, An. Sti. Univ. “Al. I. Cuza” Iasi Sect. I a Mat. 19 (1973), 365–383.
3. V. Barbu, On a nonlinear Volterra integral equation on a Hilbert space, SIAM J. Math. Anal., 8 (1977), 346–355.
4. V. Barbu, Existence for nonlinear Volterra equations in Hilbert spaces, SIAM J. Math. Anal., 10 (1979), 552–569.
5. V. Barbu, G, Da Prato and M. Iannelli, Stability results for some integro-differential equations of hyperbolic type in Hilbert space. Report UTM 39 (1979), Department of Mathematics, Libera Universita di Trento.