Left: VLT/FORS2 observed spectrum of SDSS1256 (black line). Overplotted in red is the synthetic spectrum from the NextGen atmosphere models of Baraffe et al. (1998) generated with the DUST546 code of Pavlenko et al. (2007a), which provides the best fit to the data (a low-resolution version is shown for plotting purposes). The synthetic spectra, convolved by the instrument profile, have been generated for a metallicity of [M/H] = −2.0, gravity of log g = 5.0, Li abundance of log N(Li) = − 1.0. Both spectra are normalised to the observed spectrum around 7050 Å. Major lines and features present in optical spectra of metal-poor dwarfs are shown as well. Right: zoom-in on the region around the lithium doublet at 6707.8 Å. The observed spectrum is shown in black while synthetic spectra with different Li abundances are shown in colour.