\input zb-basic \input zb-ioport \iteman{io-port 05937557} \itemau{Boizot, Nicolas; Busvelle, Eric} \itemti{Adaptive-gain observers and applications.} \itemso{Besan\c con, Gildas (ed.), Nonlinear observers and applications. Papers based on the presentations at the 28th Grenoble international summer school on control, Grenoble, France, September 2007. Berlin: Springer (ISBN 978-3-540-73502-1/pbk). Lecture Notes in Control and Information Sciences 363, 71-114 (2007).} \itemab From the introduction: Our purpose is to present a uniform framework where nonlinear filtering, empirical observers and exponentially converging observers are compared. We mainly discuss their similarities, and we propose an observer based on empirical observers (as those used by engineers), which is an exponentially converging observer. \itemrv{~} \itemcc{} \itemut{observers for nonliner systems; nonlinear system; extended Kalman filter; approximation; state knowing observations} \itemli{doi:10.1007/978-3-540-73503-8\_3} \end