The source 0218+357 is a gravitationally lensed AGN which we do not
include in our statistical analysis.
e =
The complex source 0316+413 (3C 84) satisfies our selection criteria,
but was observed as part of a separate monitoring program
Walker et al. (2000ApJ...530..233W). It is included in our statistical
analysis for completeness.
f =
Source has large or diffuse structures that are not adequately sampled
by our observations.