The discovery of the "21" μm and "30" μm emission features in Planetary Nebulae with Wolf-Rayet central starsS. Hony, L. B. F. M. Waters and A. G. G. M. TielensA&A, 378 2 (2001) L41-L44DOI: https://doi.org/10.1051/0004-6361:20011264
