Previously it has been shown that some classes of mixing dynamical systems
have limiting return times distributions that are almost everywhere Poissonian.
Here we study the behaviour of return times at periodic points and show that
the limiting distribution is a compound Poissonian distribution. We also derive
error terms for the convergence to the limiting distribution. We also prove a
very general theorem that can be used to establish compound Poisson
distributions in many other settings.Comment: 18 page