AIPS HELP file for SOURCES in 31DEC18
As of Sun Sep 23 7:50:12 2018
Type: Adverb (String*16, 30 elements)
Use: Standard data selection adverb, used to specify a list of
sources to be included in or excluded from an operation.
If the first character of ANY element is "-" then all
named sources are excluded else all named are included.
All must be left justified. All blanks mean all sources
Null Value: ' '
All null value usually means take all sources; null values
after a non null value are ignored.