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2. Determination of the density and mechanical strength of the surface layer of the lunar soil at the landing site of the Luna 13 probe;Cherkasov;Kosmich. Issled. Akad. Nauk. SSSR,1967
3. Soil-density penetrometer of the automatic lunar station Luna 13;Cherkasov;Dokl. Akad. Nauk. SSSR,1968
4. Choate , R. Lunar surface mechanical properties Surveyor VH: A Preliminary Report 41 95 Washington, D.C. 1968