Spectral classification of the mass donors in the high-mass X-ray binaries EXO 1722-363 and OAO 1657-415A. B. Mason, J. S. Clark, A. J. Norton, I. Negueruela and P. RocheA&A, 505 1 (2009) 281-286DOI: https://doi.org/10.1051/0004-6361/200912480
