Measurements of mechanical vibrations in a solid aluminium sphere and bar excited by 0.5gev electrons - G. D. van Albada; H. van der Graaf; G. Heijboer; J. W. van Holten; W. J. Kasdorp; J. B. van der Laan; L. Lapikas; G. J. L. Nooren; C. W. J. Noteboom; J. E. J. Oberski; H. Z. Peek; A. Schimmel; et al. (Proc. 2nd Amaldi conference, Geneva, July 1997, 1999)