  The likelihood of detecting individual discrete sources of cosmic rays
depends on the mean separation between sources. The analysis here derives the
minimum separation that makes it likely that the closest source is detectable.
For super-GZK energies, detection is signal limited and magnetic fields should
not matter. For sub-GZK energies, detection is background limited, and
intergalactic magnetic fields enter the analysis through one adjustable
parameter. Both super-GZK and sub-GZK results are presented for four different
types of sources: steady isotropic sources, steady jet sources, isotropic
bursts, and jet bursts.
