Notice that even when f = 1, the evolution system (4.27View Equation, 4.28View Equation, 4.20View Equation, 4.21View Equation) is not equivalent to the harmonic system discussed in Section 4.1. In the former case, the harmonic constraint is exactly enforced in order to obtain evolution equations for the lapse and shift; while in the latter case first derivatives of the harmonic constraint are combined with the Hamiltonian and momentum constraints; see Eq. (4.13View Equation).