FRONSDAL, C. . Theory of sounds in He II. ФІЗИКА НИЗЬКИХ ТЕМПЕРАТУР, Харків, Україна, v. 49, n. 2, p. 167–173, 2022. Disponível em: http://80.92.230.95/index.php/fnt/article/view/8967. Acesso em: 11 лис. 2025.