Solving the inhomogeneous Bethe–Salpeter equation in Minkowski space: the zero-energy limit Tobias Frederico, Giovanni Salmè and Michele Viviani Eur. Phys. J. C, 75 8 (2015) 398 Published online: 28 August 2015 DOI: 10.1140/epjc/s10052-015-3616-1