Le, Tan Sang, et al. “[RETRACTED] A Study on the Effect of Tool-Path Strategy When Machining a Saddle-Free Surface in 3-Axis CNC Machine”. International Journal on Advanced Science, Engineering and Information Technology, vol. 10, no. 6, Dec. 2020, pp. 2320-7, doi:10.18517/ijaseit.10.6.13054.