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		| Paper: | Hydrogen Deficient Donors in Low-Mass X-ray Binaries |  
		| Volume: | 391, Hydrogen-Deficient Stars |  
		| Page: | 273 |  
		| Authors: | Nelemans, G. |  
		| Abstract: | A number of X-ray binaries (neutron stars or black holes accreting from a companion star) have such short orbital periods that ordinary, hydrogen rich, stars do not fit in. Instead the mass-losing star must be a compact, evolved star, leading to the transfer of hydrogen deficient material to the neutron star. I discuss the current knowledge of these objects, with focus on optical spectroscopy. |  
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