√(-_g_) = 1
Here the variations vanish at the limits of the finite four-dimensional
integration-space considered.
It is first necessary to show that the form (47a) is equivalent to
equations (47). For this purpose, let us consider H as a function of
_g_^{μν} and _g_^{μν}_{σ} (= ∂_g_^{μν}/∂_x__{σ})