The circumstellar dust shell of the post-AGB star HD 161796 S. N. Hoogzaad, F. J. Molster, C. Dominik, L. B. F. M. Waters, M. J. Barlow and A. de Koter A&A, 389 2 (2002) 547-555 Published online: 27 June 2002 DOI: 10.1051/0004-6361:20020403