Before revision:   Next, we introduce a  space-time (tensorproduct) discretization using finite elements in space and piecewise linear functions in time . This setting is known to be equivalent to a Crank-Nicolson time stepping scheme for parabolic problems.
After revision:  Next, we introduce a space-time (tensorproduct) discretization using finite elements in space and piecewise linear functions in time , this setting is known to be equivalent to a Crank-Nicolson time stepping scheme for parabolic problems.