“…It is obtained by copying the dynamics (1) and using a gain P (∂h/∂x) R −1 , that mimics the Kalman-Bucy filter gain for linear systems ( [15], [16]), where the linear dynamics matrices are simply replaced by the linearized pair (∂f /∂x, ∂h/∂x) around the only available estimate (x, u). Unfortunately, apart from specific triangular structures [10], [17], only local convergence of the estimation error x − x can be ensured, under the additional ad-hoc assumption that there exist p, p > 0 such that (see [3], [5], [24], [25], [28])…”