The properties of ten O-type stars in the low-metallicity galaxies IC 1613, WLM, and NGC 3109 F. Tramper, H. Sana, A. de Koter, L. Kaper and O. H. Ramírez-Agudelo A&A, 572 (2014) A36 Published online: 25 November 2014 DOI: 10.1051/0004-6361/201424312