1. A. L. Buchachenko and A. M. Vasserman, Stable Radicals [in Russian], Khimiya, Moscow (1973).
2. M. M. Mestechkin, The Density-Matrix Method in Molecular Theory [in Russian], Naukova Dumka, Kiev (1977).
3. G. M. Zhidomirov, P. V. Schastnev, and N. D. Chuvylkin, Quantum-Chemical Calculations on Magnetic-Resonance Parameters [in Russian], Nauka, Novosibirsk (1978).
4. Localization and Delocalization in Quantum Chemistry [Russian translation], Mir, Moscow (1978).
5. A. A. Ovchinnikov, I. I. Ukrainskii, and G. F. Kventsel', Usp. Fiz. Nauk,108, 81 (1972).