Determination of the up/down-quark mass within QCD sum rules in the scalar channel Fang-Hui Yin, Wen-Ya Tian, Liang Tang and Zhi-Hui Guo Eur. Phys. J. C, 81 9 (2021) 818 Published online: 15 September 2021 DOI: 10.1140/epjc/s10052-021-09599-3