The underlying stellar absorption contribution to the primordial helium   abundance determination
  We carried out an exploratory analysis of the contribution of the underlying stellar absorption to the total uncertainty of the abundance of primordial helium using simple stellar populations models and observational data from the Sloan Digital Sky Survey. Results indicate that our analysis yields a lower limit to the error on the helium abundance determination if the stellar absorption is neglected. 
F. F. Rosales-Ortega, R. Terlevich, E. Bertone, M. Chavez (INAOE,   Mexico)
astro-ph.CO