Reference request: Nonlinear dynamics graduate reference There are already a number of requests for textbooks detailing nonlinear stability theory, chaos theory etc. but many of them are more introductory (e.g. Strogatz - Nonlinear Dynamics and Chaos)
I've covered all this material before but I'm prone to forgetting the details. I hoped somebody might be able to point me in the direction of a more formal reference text on this subject. Perhaps a graduate level text, that covers major undergraduate material in a fairly mathematically rigorous way, as well as a little extra?

"Nonlinear Oscillations, Dynamical Systems ,and Bifurcation of Vector Fields" by John Guckenheimer and Philip Holmes comes to mind. I took a class on Dynamical Systems with the first author many years ago and this was the text. I see people using the book by Strogatz and always feel that it is just not at the same level.
