A New Approach to Modelling the Drilling Torque in Conventional and Ultrasonic Assisted Deep-Hole Drilling Processes oleh Ngoc-Hung Chu, Dang-Binh Nguyen, Nhu-Khoa Ngo, Van-Du Nguyen, Minh-Duc Tran, Ngoc-Pi Vu, Quoc-Huy Ngo, Thi-Hong Tran