**Hubble's
1929 velocity-distance relation for 46 nebulae. The black dots and the
solid line represent the solution obtained from the 24 nebulae for which
individual distances were determined, using them separately. Empty circles
and the dashed line represent the solution obtained by combining the
nebulae into groups. The cross represents the mean velocity for a set
of 22 nebulae whose distances could not be estimated individually.**

*Publications
of the National Academy of Sciences* vol. **15** (1929):
168-173