Yves Coudène. Ergodic Theory and Dynamical Systems. Page 14.
Roughly speaking he mentioned that the Khintchine's Recurrence Theorem is a generalisation of Poincaré's Recurrence Theorem.
How can Khintchine's Recurrence Theorem be considered to be a generalisation of Poincaré's Recurrence Theorem.
While Poincaré's recurrence theorem refers to single orbits, Khintchine recurrence theorem refers to configurations and yields a quite optimistic conclusion about the possibility to recover the initial state of a configuration from a sequence of observations. In fact, it asserts the nonexistence of wandering configurations.