“…We recall that the Källén-Lehmann spectral integral allows only for branch cuts along the negative real axis, while certain analytical approaches, or fits to lattice data based thereon, entail the presence of e.g. complex conjugate poles, in se incompatible with the Källén-Lehmann spectral structure [17,30,31,32,28,33,34]. As a future improvement of our method, such complex conjugate poles could therefore be included in the inversion method.…”