1. The diffraction of electro-magnetic waves by a sphere located in a half-space;D'Yakonov;Bull. Acad. Sci. USSR, Geophys. Ser.,1959
2. Hill , D. A. 1970 Electromagnetic scattering concepts applied to the detection of targets near the ground 90 100 Columbus, Ohio
3. Electromagnetic scattering of a small spherical obstacle near the ground;Hill;Can. J. Phys.,1972