BACKWARD WAVE PHONON ECHOES AT 17 GHz IN SINGLE CRYSTALS OF LiTaO3, LiNbO3 AND Bi12SiO20 D.J. Meredith, J.A. Pritchard et J.K. Wigmore J. Phys. Colloques, 42 C6 (1981) C6-870-C6-872 DOI: 10.1051/jphyscol:19816258