1. Strengthening of Sapphire by Precipitates Containing Titanium
2. 2J. N. Burdick, and J. W. Glenn , "Synthetic Star Rubies and Star Sapphires and Process for Producing Same," U.S. Pat. 2,488,507, Nov. 15, 1949 .
3. 3E. W. White , "Chemical Characterization of Materials by X-Ray Spectroscopy "; Ph.D. Thesis , The Pennsylvania State University, University Park, Pa., June1965 .
4. Aluminum Oxide-Titanium Oxide Solid Solution