“…Existence results for parabolic equations with functionals of the unknown function and its spatial first-order derivatives were considered in [14] as fixed points of suitable integral operators. Our research into existence and uniqueness of such solutions for various parabolic differential-functional problems has gradually developed by the use of iterative methods or the Banach contraction principle (see [3,5,10,11]). In all these works estimates of the fundamental solutions based on [6,9,12,18] are applied.…”