SINGULAR EFFECTS IN PHONON FOCUSING ; FORMATION OF PHONON FOCUSINGCAUSTICS J. C. Hensel, R. C. Dynes, F. C. Unterwald et A. L. SimonsJ. Phys. Colloques, 42 C6 (1981) C6-212-C6-214DOI: https://doi.org/10.1051/jphyscol:1981661