W. WSZOŁEK and M. KŁACZYŃSKI, “Estimation Of The Vocal Folds Vibration Fundamental Frequency by Higer Order Spectrum”, Arch. Acoust., vol. 33, no. 4(S), pp. 183–188, Dec. 2008, Accessed: Jan. 18, 2026. [Online]. Available: https://acoustics.ippt.gov.pl/index.php/aa/article/view/856