THE SPECTROSCOPY OF SURFACE PHONONS BY INELASTIC ATOM SCATTERING G. Benedek, G. Brusdeylins, R.B. Doak and J.P. Toennies J. Phys. Colloques, 42 C6 (1981) C6-793-C6-800 DOI: 10.1051/jphyscol:19816234