2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/56912We give a proof of a theorem by N.N. Nekhoroshev concerning Hamiltonian systems with $n$ degrees of freedom and $s$ integrals of motion in involution, where $1 \le s \le n$. Such a theorem ensures persistence of $s$-dimensional invariant tori under suitable nondegeneracy conditions generalizing Poincaré's condition on the Floquet multipliers.13 pages, no figuresMathematical PhysicsDynamical Systemstext