Papers to read:

"Adaptive dynamic surface control: a simplifed algorithm for adaptive
backstepping control of nonlinear systems" by P. Yip, J.K. Hedrick

"Robust stabilization and ultimate boundedness of dynamic surface control systems via convex optimization" by B. Song, J.K. Hedrick, A. Howell

"Dynamic Surface Control for a Class of Nonlinear Systems" by D. Swaroop, J.K. Hedrick, P.P. Yip, J.C. Gerdes

"Robust Discrete-Time Variable Structure Control Methods" by J. Kim, S. Oh, D. Cho

"On Sliding Observers for Nonlinear Systems" by J. Slotine, J.K Hedrick, E.A. Misawa

"Observer Design for a Class of Nonlinear Systems" by Raghavan, S., and Hedrick, J. K

Misawa, E., and Hedrick, J. K., "Nonlinear Observers: A State-of-the-Art Review," ASME Trans., Journal of Dynamic Systems, Measurement and Control , Sept. 1989.