On the origin of the 19.5 m feature - Identifying circumstellar Mg-Fe-oxidesTh. Posch, F. Kerschbaum, H. Mutschke, J. Dorschner and C. JägerA&A, 393 1 (2002) L7-L10DOI: https://doi.org/10.1051/0004-6361:20021127