1. Aivazyan, S. A. et al. (1989) Applied Statistics. Classification and Reduction of Dimensionality [in Russian]. FiS, Moscow.
2. Aizerman, M. A., Braverman, E. M. and Rozonoer, L. I. (1970) The Method of Potential Functions in Machine Learning Theory [in Russian]. Nauka, Moscow.
3. Bognar, J. (1974) Indefinite Inner Product Spaces. Springer-Verlag, New York.
4. Braverman, E. M. (1970) Methods of extremal grouping of parameters and problem of apportionment of essential factors [in Russian]. Avtomat. i Telemekh. 1, 123–132.
5. Braverman, E. M. et al. (1971) Diagonalization of the relation matrix and detecting hidden factors [in Russian]. Trans. Inst. of Control Sciences. 1st Issue ‘Problems of increasing of automata possibilities.” ICS, Moscow, 42–79.