The BRST-invariant vacuum state of the Gribov–Zwanziger theoryD. Dudal, C. P. Felix, L. F. Palhares, F. Rondeau and D. VercauterenEur. Phys. J. C, 79 9 (2019) 731DOI: https://doi.org/10.1140/epjc/s10052-019-7235-0