Nayak, Bijan Bihari, et al. “Purple Coloured Natural Ruby: X-Ray Photoelectron Spectroscopy, X-Ray Diffraction, X-Ray Tomography and Other Microstructural Characterizations”. International Journal of Sciences: Basic and Applied Research (IJSBAR), vol. 25, no. 2, Feb. 2016, pp. 94-114, https://www.gssrr.org/JournalOfBasicAndApplied/article/view/5123.