On smoothness of a fundamental solution to a second order hyperbolic equation

@article{Romanov2009OnSO,
  title={On smoothness of a fundamental solution to a second order hyperbolic equation},
  author={Vladimir G. Romanov},
  journal={Siberian Mathematical Journal},
  year={2009},
  volume={50},
  pages={700-705}
}
We consider the problem of constructing a fundamental solution to a second order hyperbolic linear equation with variable coefficients depending on the space variable x ∈ ℝn. Under the assumption of high but finite smoothness of the coefficients, we write out the structure of a fundamental solution, establish smoothness of the coefficients of the expansion of its singular part, and characterize smoothness of the regular part.