Laroche, C., M.-J. Ross, L. Lefebvre, R. Laraocque, R. Hetu, and A. L’Esperance. “Sound Propagation of Reverse Alarms Used on Heavy Vehicles”. Canadian Acoustics, vol. 21, no. 3, Sept. 1993, pp. 29-30, https://jcaa.caa-aca.ca/index.php/jcaa/article/view/759.