Surface abundances of CNO in Galactic O-stars: a pilot study with FASTWIND L. P. Carneiro, J. Puls, T. L. Hoffmann, G. Holgado and S. Simón-Díaz A&A, 623 (2019) A3 Published online: 25 February 2019 DOI: 10.1051/0004-6361/201833738