V. Elias et al., FINITE-ENERGY SUM-RULES AND INSTANTONS IN THE INSTANTON LIQUID MODEL, Journal of physics. G, Nuclear and particle physics, 24(1), 1998, pp. 267-269
We obtain the imaginary part of the direct single-instanton contributi
on to the pseudoscalar correlator, as defined by the appropriate dispe
rsion relation, in order to derive an explicit integral representation
for the instanton contribution to finite energy sum rules in the inst
anton liquid model.