Before revision:  points \mathcal{I_0 where dx_o{d\mathcal{I}}(\mathcal{I}} _0. Stability implies that there is a stable equilibrium X(\mathcal{I})
After revision:  points \mathcal{I_0 where dx_o{d\mathcal{I}}(\mathcal{I}} is defined by a stable equilibrium X_0 at \mathcal{I_0. Stability implies that there is a stable equilibrium X(\mathcal{I})