Zhang et al. developed a methodology to extract six features from a certain interval of the time domain, where the interval itself was selected based on correlation metrics to the SoC. Li et al. extracted eleven features using both the time and the frequency domain, and then downselected seven of those, also based on their correlation and sensitivity to the SoC. Galiounas et al. had previously demonstrated that the frequency domain contains useful structures and that time-domain features could be filtered down. In a study on cylindrical cells, Montoya-Bedoya et al. extracted parameters from the power spectrum, highlighting a particular parameter called the 'mid-band fit'. This was computed by performing a line-fitting operation on the normalised power spectrum which, according to the authors, is a method used in medical applications.