2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/83483The Surface Green Function Matching analysis (SGFM) is used to study the normal modes of the interface oscillations between two non-mixed fluids by considering the difference in their densities and viscosities. The limiting case of viscous-inviscid system is used for comparison. The role of the viscosity and the density ratios on the momentum exchange and on the polarization of the surface modes is analyzed.8 pages, 6 .eps figures. Appeared in Phys. Scripta 59, 313-318 (1999)Fluid Dynamicstext