S.M, Daniliev, and Danilieva N.A. “Frequency Components of Radargrams in Analyses of Shallow Soil Cavities”. International Journal of Engineering & Technology 7, no. 2.13 (April 15, 2018): 127–132. Accessed July 6, 2024. https://sciencepubco.com/index.php/ijet/article/view/11625.