1. E. O. Hall, “Deformation and ageing of mild steel,” Proc. Phys. Soc. B 64 (1), 747–753 (1951).
2. N. J. Petch, “The cleavage strength of polycrystals,” J. Iron Steel Inst. 174, 25–28 (1953).
3. T. Christman, “Grain boundary strengthening exponent in conventional and ultrafine microstructures,” Scripta Metall. Mater. 28, 1495–1500 (1993).
4. A. H. Cottrell, “Discontinuous yielding,” in The Relation between the Structure and Mechanical Properties of Metals (Her Majesty’s Stationary Office, London, 1963), pp. 456–473.
5. P. W. Armstrong, “Strength properties of ultrafinegrain metals,” in Proceedings of Sixteenth Sagamore Army Materials Research Conference on Ultrafine-Grain Metals, Ed. by J. J. Burke and V. Weiss (Syracuse University Press, New York, 1970), pp. 9–37.