1. P. Muthukumar and P. Balasubramaniam, Approximate controllability of mixed stochastic Volterra–Fredholm type integrodifferential systems in Hilbert space, Journal of the Franklin Institute, vol.348, no.10,  2011, pp.2911–2922, http://dx.doi.org/10.1016/j.jfranklin.2011.10.001