Evidence for a 2:3 resonance in Sco X-1 kHz QPOs
  We find evidence that the two high frequency QPOs in Sco X-1 are, more often than not, approximately in the 2:3 frequency ratio familiar from studies of black hole candidates (e.g., XTE J1550-564, Remillard et al. 2002). This implies that the double kHz QPO phenomenon in neutron stars has its origin in properties of strong-field gravity and has little to do with the rotation of a stellar surface or any magnetic field structure anchored in the star. 
M.A. Abramowicz, T. Bulik, M. Bursa, W. Kluzniak