Massive Star Evolution: What we do (not) know
  The modelling of massive star evolution is a complex task, and is very sensitive to the way physical processes (such as convection, rotation, mass loss, etc.) are included in stellar evolution code. Moreover, the very high observed fraction of binary systems among massive stars makes the comparison with observations difficult. In this paper, we focus on discussing the uncertainties linked to the modelling of convection and rotation in single massive stars. 
Cyril Georgy, Raphael Hirschi and Sylvia Ekstr\"om
astro-ph.SR