Sub-surface convection zones in hot massive stars and their observable consequences M. Cantiello, N. Langer, I. Brott, A. de Koter, S. N. Shore, J. S. Vink, A. Voegler, D. J. Lennon and S.-C. Yoon A&A, 499 1 (2009) 279-290 Published online: 12 March 2009 DOI: 10.1051/0004-6361/200911643