The Primordial helium abundance from observations of extragalactic H-II regions

@article{Pagel1992ThePH,
  title={The Primordial helium abundance from observations of extragalactic H-II regions},
  author={Bernard Ephraim Julius Pagel and E. A. Simonson and Roberto Terlevich and Michael Edmunds},
  journal={Monthly Notices of the Royal Astronomical Society},
  year={1992},
  volume={255},
  pages={325-345}
}
The pre-galactic (assumed primordial) helium mass fraction Y p is determined to be 0.228 ± 0.005 (s.e.) or Y p < 0.242 with 95 per cent confidence, taking reasonably likely systematic errors into account. This is based on INT and AAT observations of emission lines from H II galaxies combined with selected data from the literature relating to extragalactic H II regions in general, discussed in a consistent analysis taking into account the known corrections and likely sources of error 
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