. . "Liquid He" . . "Liquid helium" . "liquefied helium" . . . . "⁴He" . . "liquifying helium" . . "liquid" . "liquid helium" . . "helium liquifier" . "Liquid Helium" . "liquid Helium" . "Helium" . . . . "Helium liquifier" . "helium-cooled" . . . . . "helium liquid" . "Four Kelvin" . "LHe" . "Liquid helium" . . "Helium Liquefiers" . . . . . . . . "highly unusual liquid" . . . . . . "helium" . . . . "liquified helium" . .