This book contains the lecture series originally delivered at the
Advanced Course on Limit Cycles of Differential Equations in the Centre
de Rechercha Mathematica Barcelona in 2006. It covers the center-focus
problem for polynomial vector fields, and the application of abelian
integrals to limit cycle bifurcations. Both topics are related to the
authors' interests in Hilbert's sixteenth problem, but would also be of
interest to those working more generally in the qualitative theory of
dynamical systems.