Locally optimal and robust backstepping design. - Kenan Ezal; Zigang Pan; Petar V. Kokotovic (IEEE Trans. Autom. Control., 2000)

Disturbance attenuating output-feedback control of nonlinear systems with local optimality. - Kenan Ezal; Petar V. Kokotovic; Andrew R. Teel; Tamer Basar (Autom., 2001)

Backstepping design with local optimality matching. - Zigang Pan; Kenan Ezal; Arthur J. Krener; Petar V. Kokotovic (IEEE Trans. Autom. Control., 2001)