Zawieska, W.M., and W.P. Rdzanek. “Low Frequency Approximation of Mutual Modal Radiation Efficiency of a Vibrating Rectangular Plate”. Archives of Acoustics, vol. 31, no. 4(S), Jan. 2014, pp. 123-30, https://acoustics3.ippt.pan.pl/index.php/aa/article/view/1332.