“…Thus (see Pazy [29], p. 185), system () admits a unique mild solution y ( t ) which depends continuously on y 0 and is defined for all t ≥ 0 by (). Moreover, following the same techniques as in previous research [14, 17], one can show that y satisfies the estimate for all 0 ≤ s ≤ t ≤ T and for all y 0 ∈ X . In particular, we have …”