Uncertainties in stellar evolution models: convective overshoot
  In spite of the great effort made in the last decades to improve our understanding of stellar evolution, significant uncertainties remain due to our poor knowledge of some complex physical processes that require an empirical calibration, such as the efficiency of the interior mixing related to convective overshoot. Here we review the impact of convective overshoot on the evolution of stars during the main Hydrogen and Helium burning phases. 
Alessandro Bressan, Leo Girardi, Paola Marigo, Philip Rosenfield, and   Jing Tang
astro-ph.SR