Muñoz, A., J. Castaing, and A. Domínguez-Rodríguez. 2001. “Effect of Dislocation Density on the Rhombohedral Twinning Stress of Sapphire (α-Al2O3)”. Revista De Metalurgia 37 (2):285-89. https://doi.org/10.3989/revmetalm.2001.v37.i2.482.