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Almost all previous radio variability studies have been based on source lists of limited size and chosen in an ad hoc manner. In contrast, the present survey of variability is based on a far larger sample and examines variability in a population of much weaker sources, and therefore possibly of a different nature. The Parkes-MIT-NRAO 4850-MHz survey of the southern sky (Wright et al. 1994, Ap. J. Suppl. 91, p. 111) produced a large catalog of sources south of declination -37 deg. We have examined about 11,000 of these sources (galactic latitude > 10 deg, flux density > 40 mJy) for their interday variability when observed in June 1990. This was possible because the observing protocol of the survey led to any given patch of sky (and therefore any catalogued source) being scanned from 4 to 9 times over a two-week period. Using three different criteria we have studied the degree of variability exhibited by each source and have identified about 170 possibly variable sources. Examples of these sources will be shown.
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