Reference marks method for the determination of wear of machine parts: M. M. Khruschov and E. S. Berkovich (Academic Press of the U.S.S.R., Moscow, 1959) 218 pp. (in Russian); 23 × 16 cm; 21 tables, 113 figs. and photographs; 50 ref. of which 43 refer to contributions of workers in the U.S.S.R.; 10.25 Roubles