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		| Paper: | 
		The Wolf-Rayet Hydrogen Puzzle – an Observational Point of View | 
	 
	
		| Volume: | 
		353, Stellar Evolution at Low Metallicity: Mass Loss, Explosions, Cosmology | 
	 
	
		| Page: | 
		197 | 
	 
	
		| Authors: | 
		Foellmi, C.; Marchenko, S.V.; Moffat, A.F.J. | 
	 
	
	
		| Abstract: | 
		Significant amounts of hydrogen were found in very hot early-type single WN stars in the SMC and the LMC. Recently, we found similar evidence in the Wolf-Rayet star of a short-period LMC binary. We discuss here the relevance of hydrogen for WR star classification, models, the relation to metallicity, and the GRB progenitors. | 
	 
	
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