1. A. L. Buchachenko and A. M. Vasserman, Stable Radicals [in Russian], Khimiya, Moscow (1973).
2. D. Kivelson, J. Chem. Phys., 33, No. 4, 1094–1106 (1960).
3. A. Abragam and B. Bleaney, Electron Paramagnetic Resonance of Transition Ions, V. 1, 602–647, Clarendon Press, Oxford (1970).
4. I. B. Bersuker, The Jahn-Teller Effect, Cambridge University Press (2006).
5. V. A. Nadolinny, A. A. Pavlyuk, A. A. Ryadun, S. F. Solodovnikov, Z. A. Solodovnikova, E. S. Zolotova, V. F. Plusnin, M. I. Rakhmanova, and E. G. Boguslavsky, Functional Materials, 18, No. 3, 368–374 (2011).