  The series expansion formulae are established for the one- and two-center
charge densities over complete orthonormal sets of exponential type orbitals
introduced by the author. Three-center overlap integrals of appearing in these
relations are expressed through the two-center overlap integrals between
-orbitals. The general formulae obtained for the charge densities are utilized
for the evaluation of arbitrary multicenter-multielectron integrals occurring
when the complete orthonormal sets of exponential type orbitals are used as
basis functions in the Hartree-Fock-Roothaan and explicitly correlated methods.
The relationships for charge densities and multicenter-multielectron integrals
obtained are valid for the arbitrary quantum numbers, screening constants and
location of orbitals.
