J. Shao, T. Wang, H. Yin, D. Yang, and Y. Li, “Bolt Looseness Detection Based on Piezoelectric Impedance Frequency Shift,” Appl. Sci., vol. 6, no. 10, p. 298, Oct. 2016.
C. H. Zhong, A. J. Croxford, and P. D. Wilcox, “Remote inspection system for impact damage in large composite structure,” Proc. R. Soc. A, vol. 471, no. 2173, p. 20140631, Jan. 2015.