Forshaw, S., L. Ritmiller, M. Hodgson, and C. Laroche. “Estimates of Speech Intelligibility Based on Equivalent Speech- and Noise-Spectrum Levels and Hearing Thresholds”. Canadian Acoustics, vol. 27, no. 3, Sept. 1999, pp. 112-3, https://jcaa.caa-aca.ca/index.php/jcaa/article/view/1243.