Q-Factor Measurement of Nonlinear Superconducting Resonators
  A novel method, which combined a multi-bandwidth measurement and an extrapolation procedure, is proposed for extracting the loaded Q-factor (Q_{L}) with improved accuracy from non-Lorentzian resonances of nonlinear superconducting resonators. 
X. S. Rao, C. K. Ong and Y. P. Feng