  A field-theoretical representation is suggested for the electron global
density of states distribution function P(\nu) in extended disordered
conductors. This opens a way to study the complete statistics of fluctuations.
The approach is based on a functional integration over bi-local functions
\Psi(r_1, r_2) instead of the integration over local functions in the usual
functional representation for moments of physical quantities. The formalism
allows one to perform the disorder averaging and to derive an analog of the
usual nonlinear sigma-model - a "slow" functional of a supermatrix field Q(r;
r_1, r_2) \sim \Psi(r, r_1) \circ \bar{\Psi}(r_2, r). As an application of the
formalism, the long-tail asymptotics of P(\nu) is derived.
