Short wave length approximation of a boundary integral operator for   homogeneous and isotropic elastic bodies
  We derive a short wave length approximation of a boundary integral operator for two-dimensional isotropic and homogeneous elastic bodies of arbitrary shape. Trace formulae for elastodynamics can be deduced in this way from first principles starting directly from Navier-Cauchy's equation. 
Gregor Tanner and Niels Sondergaard