Evidence for a 2:3 resonance in Sco X-1 kHz QPOs M. A. Abramowicz, T. Bulik, M. Bursa and W. Kluźniak A&A, 404 1 (2003) L21-L24 Published online: 26 May 2003 DOI: 10.1051/0004-6361:20030737