sentences:  Using the auxiliary window functions formula_40 and formula_41, the reassignment operations can be computed at any time-frequency coordinate
  formula_16 from an algebraic combination of three Fourier transforms evaluated at formula_16.Since these algorithms operate only on short-time spectral data evaluated at a single time and frequency, and do not explicitly compute any derivatives, this gives an efficient method of computing the reassigned discrete short-time Fourier transform.One constraint in this method of computation is that the formula_44 must be non-zero.