Photospheric radius expansion X-ray bursts as standard candles E. Kuulkers, P. R. den Hartog, J. J. M. in 't Zand, F. W. M. Verbunt, W. E. Harris and M. Cocchi A&A, 399 2 (2003) 663-680 Published online: 07 February 2003 DOI: 10.1051/0004-6361:20021781