The R1R2' outer ring revealed by young open cluster data
  The distribution of young open clusters in the Galactic plane suggests the
existence of the outer ring R1R2' in the Galaxy. The solar position angle
theta_b providing the best agreement between the observed and model
distribution is theta_b=35 +\- 10 degrees. We compared the theta_b values
derived from three different catalogues of open cluster and they appear to be
consistent within the errors.
