A dispersion integral is derived that connects data on η → π + π − γ to the η → γγ * transition form factor. A detailed analysis of the uncertainties is provided. We find for the slope of the η transition form factor at the origin b η = 2.05

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We discuss the problem of lattice artefacts in QCD simulations enhanced by the introduction of dynamical charmed quarks. In particular, we advocate the use of a massive renormalization scheme with a close to realistic charm mass. To maintain O(a) improvement for Wilson type fermions in this case we define a finite size scheme and carry out a nonperturbative estimation of the clover coefficient c sw . It is summarized in a fit formula c sw (g 2 0 ) that defines an improved action suitable for future dynamical charm simulations.