“…From Strichartz estimates and estimate (3.10), u ∈ C([t 0 , t 0 + T ],W 1,2 L ) ∩ L q ((t 0 , t 0 + T ),W 1,p L (C n )) for every admissible pair (q, p). In view of Lemma A.1 in [6], u is also a solution to the initial value problem (1.1), (1.2). Similarly solution exists on the interval [t 0 − T ′ , t 0 ] for some T ′ > 0.…”