1. Battrick, B. 1994, in Horizon 2000 Plus: European Space Science in the 21st Century, ed. B. Battrick, ESA SP-1180, ESA, Noordwijk
2. Boden, A., Unwin, S., & Shao, M. 1997, in Hipparcos Venice 97, ed. M. A. C. Perryman, & P. L. Bernacca, ESA SP-402, ESA, Noordwijk, 789
3. Comparisons of a Galactic Kinematic Model with Two Proper‐Motion Surveys in the Vicinity of the North Galactic Pole
4. de Zeeuw, P. T. 1999, in The Third Stromlo Symposium: The Galactic Halo: Bright Stars and Dark Matter, ed. B. K. Gibson, T. S. Axelrod, & M. E. Putman, ASP Conf. Ser. 165, 515
5. ESA 2000, GAIA: Composition, Formation and Evolution of the Galaxy, Technical Report ESA-SCI(2000)4, (scientific case on-line at http://astro.estec.esa.nl/GAIA)