The long-period Galactic Cepheid RS Puppis - I. A geometric distance from its light echoes P. Kervella, A. Mérand, L. Szabados, P. Fouqué, D. Bersier, E. Pompei and G. Perrin A&A, 480 1 (2008) 167-178 Published online: 09 January 2008 DOI: 10.1051/0004-6361:20078961