A. Zhussupbekov, Y. Iwasaki, N. Shakirova, and E. Chul Shin, “CONTROL AND QUALITY OF PILES BY NON-DESTRUCTIVE EXPRESS METHODS: LOW STRAIN METHOD AND CROSS-HOLE SONIC LOGGING”, IJCCSE, vol. 15, no. 1, pp. 171–180, Mar. 2019, doi: 10.22337/2587-9618-2019-15-1-171-180.