  Some relationships, fundamental to the resolution of interface wave problems,
are presented. These equations allow for the derivation of explicit secular
equations for problems involving waves localized near the plane boundary of
anisotropic elastic half-spaces, such as Rayleigh, Sholte, or Stoneley waves.
They are obtained rapidly, without recourse to the Stroh formalism. As an
application, the problems of Stoneley wave propagation and of interface
stability for misaligned predeformed incompressible half-spaces are treated.
The upper and lower half-spaces are made of the same material, subject to the
same prestress, and are rigidly bonded along a common principal plane. The
principal axes in this plane do not however coincide, and the wave propagation
is studied in the direction of the bisectrix of the angle between a principal
axis of the upper half-space and a principal axis of the lower half-space.
