  The Anderson-Bogoliubov branch of collective excitations in a condensed Fermi
gas is treated using the effective bosonic action of Gaussian pair
fluctuations. The spectra of collective excitations are treated for finite
temperature and momentum throughout the BCS-BEC crossover. The obtained spectra
explain, both qualitatively and quantitatively, recent experimental results on
Goldstone modes in atomic Fermi superfluids.
