  This is a partly expository, partly new paper on sup norm estimates of
eigenfunctions. The focus is on the quantum completely integrable case. We give
a new proof of the main result of our paper ``Riemannian manifolds with
uniformly bounded eigenfunctions' (Duke Math J. 111 (2002), 97-132), based on
the analysis of quasi-modes and Birkhoff normal forms. We also discuss related
issues of resonant normal forms and tunnelling between tori.
