Ultrasonic study of the normal — incommensurate — commensurate phase transitions in [N(CH3)4]2ZnCl 4 J. Berger, J.P. Benoit, C.W. Garland et P.W. Wallace J. Phys. France, 47 3 (1986) 483-489 DOI: 10.1051/jphys:01986004703048300