“…For instance, Martin et al (1985) and Hellings (1986) have tried, in an essentially heuristic manner, to explicitly take into account the main apparent deformations due to the use of an external coordinate representation. More recently a notable progress in the theory of such local relativistic frames (at the post-Newtonian approximation, relevant to systems of N weakly self-gravitating bodies) has been achieved by Brumberg and Kopejkin (1988a,b) (Kopejkin, 1988;Brumberg, 1990) in a series of publications (see also Voinov, 1988). Their approach combines the usual post-Newtonian-type expansions with the multipole expansion formalisms for internally generated (Thome, 1980;Blanchot andDamour, 1986, 1989) and externally generated (Thorne and Hartle, 1985), gravitational fields, and with asymptotic matching techniques (D'Eath, 1975, Damour, 1983.…”