SECOND SOUND IN A WEAKLY IDEAL BOSE GAS

ON THEORY OF NON-IDEAL BOSE GAS

DENSITY EXCITATIONS OF WEAKLY INTERACTING BOSE GAS

Problem of Second Sound in a Nonideal Bose Gas

First and second sound in a weakly interacting dilute Bose gas

Observation of First and Second Sound in a Homogeneous Bose Gas

Second Sound in a Slightly Nonideal Bose Gas