1. I. L. Chernyak and S. A. Yarunin, Control of Rock Mass State [in Russian], Nedra, Moscow (1995).
2. Yu. N. Baukov and V. N. Danilov, ?Physical foundations of the resonance method for controlling foliations in the roof of mine workings,? Izv. Vuzov, Gorn. Zh., No. 1 (1988).
3. M. D. Molev, Geophysical Prediction of Mining and Geological Conditions for Underground Mining of Coal Seams [in Russian], YuRGTU, Novocherkassk (2000).
4. V. S. Yamshchikov, E. E. Sidorov, and Yu. N. Baukov, ?Vibroacoustic method for controlling quality of layered constructions,? Defektoskopia, No. 5 (1978).
5. A. G. Glikman, ?Elastic waves in layered media,? in: Collected Works of the VNIIG [in Russian], Leningrad (1986).