1. S. Batsanov, Structural Chemistry. Book of Facts. [in Russian], Dialog-MSU, Moscow (2000).
2. S. Batsanov, Neorg. Mater., 37, 1031–1046 (2001).
3. R. W. F. Bader, Atoms in Molecules: A Quantum Theory, International Series of Monographs on Chemistry 22, Clarendon Press, Oxford (1990).
4. T. K. Ghanty and S. K. Ghosh, J. Phys. Chem., 100, 17429–17433 (1996).
5. G. V. Gibbs, O. Tamada, and M. B. Jr. Boisen, Phys. Chem. Minerals., 24, 432–439 (1997).