S-stars motion around relativistic compact object Sgr A*
  A review of modern VLTI observations of the orbital motion of closest stars
to the relativistic compact object Sgr A* and its ability to test gravitation
theories in the conditions of Post-Newtonian approximation. The observed
orbital parameters, second order Doppler effect and gravitational redshift,
measured for several S-stars, are compared with theoretical PN predictions.
