Gies, D. R., Bolton, C. T., Blake, R.M., Caballero-Nieves, S.M., Crenshaw, D. M., Hadrava, P., Herrero, A., Hillwig, T.C., Howell, S.B., Huang, W., Kaper, L., Koubský, P., McSwain, M.V. Stellar Wind Variations during the X-Ray High and Low States of Cygnus X-1. Astrophysical Journal. 2008, 678(2), 1237-1247. ISSN 0004-637X. E-ISSN 1538-4357. Available: https://doi.org/10.1086/586690