Kienlin, A. von High Energy Astrophysics, MPI for Extraterrestrial Physics, Max Planck Society;
Beckmann, V., Soldi, S., Bélanger, G., Brandt, S., Caballero-García, M. D., De Cesare, G., et al. (2007). Cygnus X-3 transition from the ultrasoft to the hard state. Astronomy & Astrophysics, 473(3), 903-905. doi:10.1051/0004-6361:20078160.