“…For f ∈ L 2 (0, T ; H −m (Ω)), h ∈ L 2 (Ω), problem (1.1) with homogeneous Neumann boundary data admits a unique weak solution u ε ∈ L 2 (0, T ; H m (Ω)) ∩ L ∞ (0, T ; L 2 (Ω)) [5]. Similar to the initial-Dirichlet problem, under the periodicity condition (1.4) u ε converges strongly in L 2 (0, T ; H m−1 (Ω)) to the solution u 0 of the following initial-Neumann problem…”