On the Choice of Dispersion Relation to Calculate the QCD Correction to   $\Gamma(H\to \ell^+\ell^-)
  We use the Operator Product Expansion (OPE) of quark vacuum polarization functions to show that the dispersion relation of Kniehl and Sirlin will yield the correct result to all orders in $\alpha_s$ when applied to the QCD correction to the leptonic decay width of the Higgs boson. 
Tatsu Takeuchi, Aaron K. Grant, and Mihir Worah