1. C. De Beer, ‘The Web Thickness of Twist Drills’, Annals of CIRP,18, 1970, p. 81.
2. G. Lorenz, ‘Helix Angle and Drill Performance’, Annals of CIRP,28, (1), 1979, p. 83.
3. G. Spur and J. R. Masuha, ‘Drilling with Twist Drills of Different Cross Section Profiles’, Annals of CIRP,30(1), 1981, p. 31.
4. C. Donaldson, G. H. LeCain and V. C. Goold, ‘Tool Design’, McGraw-Hill, 1973.