1. J. M. Baker and M. E. Newton, “Nitrogen in Diamond Studied by Magnetic Resonance,” Appl. Magn. Reson. 8(2), 207–227 (1995).
2. L. V. Bershov, A. B. Brik, and R. M. Mineeva, “Radiospectroscopic Research,” in Methods of Mineralogical Research (Nedra, Moscow, 1985), pp. 444–459 [in Russian].
3. A. T. Collins, “The Color of Diamond and How It May Be Changed,” J. Gemm. 27(6), 335–339 (2001).
4. A. Cox, M. E. Newton, and J. M. Baker, “ENDOR Studies on the N1 Di-Nitrogen Center in Diamond,” J. Phys.: Condens. Matter 4(41), 8119–8130 (1992).
5. G. Davies, “The H3 Center,” in Diamond Research (Suppl. Ind. Diamond Rev., 1977), pp. 15–24.