PACS numbers

67.40.Mj First sound

B.N. Esel’son, M.I. Kaganov et al “’Sound’ in superfluid liquids” Sov. Phys. Usp. 17 215–238 (1974)
67.40.Pm, 67.40.Mj, 67.60.−g, 67.70.+n (all)