“…This period of expansion lasted throughout the Voyager years, 1973Voyager years, -1989. While photographic techniques predominated (Pascu 1977(Pascu , 1979, this period saw the introduction of several new observational methods -in particular, mutual phenomena techniques (Millis 1974;Aksnes and Franklin 1975), space techniques (Born and Duxbury 1975;Callahan 1988, 1989), and CCD techniques (Pascu et al 1983(Pascu et al , 1987.…”