  The theory of correlated electron systems is formulated in a form which
allows to use as a reference point an ab initio band structure theory (AIBST).
The theory is constructed in two steps. As a first step the total Hamiltonian
is transformed into a correlated form. In order to elucidate the microscopical
origin of the parameters of the periodical Hubbard-Anderson model (PHAM) the
terms of the full Hamiltonian which have the operator structure of PHAM are
separated. It is found that the matrix element of mixing interaction includes
ion-configuration and number-of-particles dependent contributions from the
Coulomb interaction. In a second step the diagram technique (DT) is developed
by means of generalization of the Baym-Kadanoff method for correlated systems.
