1. E. Meyer, Zeitschrift des Vereins Deutschen Ingenieure, 52 645–654 (1908).
2. D. Tabor, The hardness of metals, (Oxford University press, Great Britain, 1951).
3. M. M. Matlin, A.I. Mozgunova, E. N. Kazankina and V.A. Kazankin, Methods of non-destructive testing of strength properties of machine parts (Mechanical engineering, Moscow, 2019), 249 p.
4. GOST 18835-73. Metals. Method of measuring plastic hardness, (Standartizdat, Moscow, 1975).
5. P. M. Ogar, V. A. Tarasov and I. B. Fedorov, Mechanics XXI cent. 12 66–70 (2013).