Affiliation: | Institute of Astronomy, Madingley Road, Cambridge CB3 0HA; California Institute of Technology, MS 105-24, Pasadena, CA 91125, USA; Pennsylvania State Univ., Dept. of Astronomy and Astrophysics, 525 Davey Lab, University Park, PA 16802, USA; Instituto de Astrofísica de Canarias, c/ Via Láctea s/n, E-38200 La Laguna, Tenerife, Spain |