First stars IX - Mixing in extremely metal-poor giants. Variation of the C-12/C-13, [Na/Mg] and [Al/Mg] ratios
Context. Extremely metal-poor (EMP) stars preserve a fossil record of the composition of the ISM when the Galaxy formed. It is crucial, however, to verify whether internal mixing has modified their surface composition, especially in the giants where most elements can be studied. Aims. We aim to understand the CNO abundance variations found in some, but not all EMP field giants analysed earlier. Mi
