Observation of second sound in NaF by means of light scatteringDieter W. PohlV. Irniger1976Physical Review Letters
All-glass vacuum-insulated liquid-nitrogen cooled CO laserE. HauptV. Irnigeret al.1982Review of Scientific Instruments
Observation of second sound by means of forced thermal scatteringDieter W. PohlV. Irniger1976Optics Communications