ACOUSTIC MODES IN Ga1-xAlxAs CRYSTALS AND RELATED SUPERLATTICES J. Sapriel, J.C. Michel, J.C. Toledano et R. Vacher J. Phys. Colloques, 45 C5 (1984) C5-139-C5-143 DOI: 10.1051/jphyscol:1984520