  In their seminal paper [Chaos 18, 037113 (2008)], E. Ott and T. M. Antonsen
showed that large groups of phase oscillators driven by a certain type of
common force display low dimensional long-term dynamics, which is described by
a small number of ordinary differential equations. This fact was later used as
a simplifying reduction technique in many studies of synchronization phenomena
occurring in networks of coupled oscillators and in neural networks. Most of
these studies focused mainly on partially synchronized states corresponding to
the equilibrium-type dynamics in the so called Ott-Antonsen manifold. Going
beyond this paradigm, here we propose a universal approach for the efficient
analysis of partially synchronized states with non-equilibrium periodic
collective dynamics. Our method is based on the observation that the Poincar\'e
map of the complex Riccati equation, which describes the dynamics in the
Ott-Antonsen manifold, coincides with the well-known M\"obius transformation.
To illustrate the possibilities of our method, we use it to calculate a
complete bifurcation diagram of travelling chimera states in a ring network of
phase oscillators with asymmetric nonlocal coupling.
