1.4. Primordial abundances
The determination of primordial abundances, which will be discussed in some detail below, requires solution of two separate problems:
1. Determination of abundances in objects that can be sampled or observed now; and 2. Extrapolation of these abundances back to pregalactic values that can be identified with products of BBNS, allowing for enhancement or destruction by astrophysical processes that may have taken place in the meantime. In what follows, I consider the separate elements and describe what has been deduced, updating previous discussions of this topic by Pagel (1982), Shaver, Kunth & Kjar (1983), Yang et al. (1984), Boesgaard & Steigman (1985) and Pagel (1987a).