  Generic Hamiltonian systems have a mixed phase space where regions of regular
and chaotic motion coexist. We present a method for constructing an integrable
approximation to such regular phase-space regions including a nonlinear
resonance chain. This approach generalizes the recently introduced iterative
canonical transformation method. In the first step of the method a normal-form
Hamiltonian with a resonance chain is adapted such that actions and frequencies
match with those of the non-integrable system. In the second step a sequence of
canonical transformations is applied to the integrable approximation to match
the shape of regular tori. We demonstrate the method for the generic standard
map at various parameters.
