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2. V. Gagov, Modern Technology and Industrial Reengineering, Varna, 1992, p. 63
3. Physical modelling studies using spike forging to verify analytical predictions
4. An analysis of closed-die extrusion/forging
5. A. Bryukhanov, A. Rebelsky, Closed Die Forging and Die Design, GNTIML, Moscow, 1962