“…In all those works, error estimates were established under certain time-step conditions. Moreover, linearized semi-implicit schemes have also been analyzed with certain time-step restrictions for many other nonlinear parabolic-type systems, such as Navier-Stokes equations [1,21,23,26,27], nonlinear thermistor problems [14,44], viscoelastic fluid flow [9,15,41], KdV equations [30], nonlinear Schrödinger equation [34,38] and some other equations [2,22,35]. A key issue in analysis of FEMs is the boundedness of the numerical solution in L ∞ norm or a stronger norm, which in a routine way can be estimated by the mathematical induction with an inverse inequality, such as,…”