Planetary ring studies have evolved from observations of a single example, (Saturn), to related studies of a class of objects, in the last several years; in fact, this is the first IUGG review article on the subject. Therefore, it seems appropriate to cite at least review articles going back beyond 1979, if only as a guide to earlier literature (Alexander 1962, Bobrov 1970, Cook et al. 1973, Palluconi and Petengill (eds) 1973, Pollack 1975, Cook and Franklin 1977, and Cuzzi 1978; all of which deal only with Saturn's rings). More recent reviews have been written by Ip (1980 a,b); Cook (1980), Elliot (1982), and Goldreich and Tremaine (1982); also of interest are review articles in books to be published shortly; Saturn (Gehreis, ed.) and Planetary Rings (Brahic and Greenberg, eds.). Popular articles of interest have been written by Pollack (1978), Burns (1981) and Pollack and Cuzzi (1982).