A high-precision abundance analysis of the nuclear benchmark star HD 20 Michael Hanke, Camilla Juul Hansen, Hans-Günter Ludwig, Sergio Cristallo, Andrew McWilliam, Eva K. Grebel and Luciano Piersanti A&A, 635 (2020) A104 Published online: 16 March 2020 DOI: 10.1051/0004-6361/201937189