We use forty B-spline basis functions to solve the Brueckner equation. The energy levels and transition amplitudes thus obtained have included the electron-electron interaction up to second order. The third order corrections are added by perturbation. The results plus the contributions from the Breit interaction and mass polarization give accurate theoretical values for energies. We then extract the contribution of radiative corrections by taking the difference of these theoretical values and available experimental data. We show that the Lamb-shift formulas derived by Feldman and Fulton do yield correct order of magnitude for Li-isoelectronic sequence.