Helmut Hofer is Professor at the Institute for Advanced Study in Princeton, New Jersey, USA. Eduard Zehnder is emeritus Professor of ETH Zurich, Switzerland.
From the reviews: Symplectic Invariants and Hamiltonian Dynamics is obviously a work of central importance in the field and is required reading for all would-be players in this game. Happily, it is very well written and sports a lot of very useful commentary by the authors; the sections introducing the individual chapters are particularly well done ... . It is all fine scholarship in an exciting and fertile area. (Michael Berg, The Mathematical Association of America, June, 2011)