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		| Paper: | Analyses of IRAS low resolution spectra of young planetary nebulae |  
		| Volume: | 9, Cool Stars, Stellar Systems, and the Sun: Sixth Cambridge Workshop |  
		| Page: | 471 |  
		| Authors: | Zhang, Cheng-Yue; Kwok, Sun |  
		| Abstract: | The 18-micron silicate feature is detected in 11 young planetary nebulae (PNe) selected from the radio properties. The presence of the 18-micron silicate feature suggests that the oxygen-rich PNe are more common than previously believed. The silicate dust probably originates from the remnants of the circumstellar envelopes of the nebulae's asymptotic giant-branch progenitors. Most interestingly, their six young PNe show both oxygen- and carbon-rich dust features. |  
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