1. J. Kopač, Hardening phenomena of austenitic steels in cutting, Ph.D. thesis, Faculty of Mechanical Engineering, Ljubljana, Slovenia, 1986.
2. Z. Seljak, Machinability of austenitic materials, Strojniški vestnik, 9–10, Ljubljana, Slovenia, 1985.
3. J. Kopač, Z. Seljak, The Influence of Heat Treatment on the Machinability of Highly Alloyed Manganese Steels, MMA’83, Novi Sad, Yugoslavia.
4. J. Kopač, Problems at Machining of Wear Resistant Austenitic Manganese Steel-12Mn, XVI savetovanje proizvodnog mašinstva Jugoslavije, Mostar, Yugoslavia, 1982.
5. J. Kopač, Z. Seljak, Material Transformation on the Cutting Edge in Machining of Austenitic Steels, XIX savetovanje proizvodnog mašinstva Jugoslavije, Kragujevac, Yugoslavia, 1985.