“…For the infinite dimensional control systems, the problem of approximate controllability is more substantial and is having broad range of applications, see for instance, [33,55,56,67], etc. In the past few decades, the problem of approximate controllability for different kinds of dynamical systems (in Hilbert and Banach spaces) such as fractional evolution equations, Sobolev type systems, delay (functional) differential equations, impulsive systems, stochastic differential equations, etc, has been widely studied by many researchers and they have produced excellent results, see for instance, [1,3,16,33,46,64] etc, and the references therein.…”