Period sets of linear toral endomorphisms on T2T2

The period set of a dynamical system is defined as the subset of all integers n such that the system has a periodic orbit of length n  . Based on known results on the intersection of period sets of torus maps within a homotopy class, we give a complete classification of the period sets of (not necessarily invertible) toral endomorphisms on the 2-dimensional torus T2T2.