Zachariasz, Radosław, and Jan Ilczuk. “Electric and Mechanical Properties of Pb(Fe$_{0.5}$Nb$_{0.5}$)O$_{3}$ Ferroelectric Ceramics”. Archives of Acoustics, vol. 32, no. 4(S), Jan. 2014, pp. 111-6, https://acoustics3.ippt.pan.pl/index.php/aa/article/view/1397.