Probing QCD Corrections to QED Effects Through Optical Experiments in   Vacuum
  A numerical estimative error of the magnitude of the vacuum polarization effect due to electron-positron by a factor of $10^3$ in [PRL97(2006)100403; 269901(E)] invalidates the study carried in this work in its present context. 
J. Dias de Deus, P. Castelo Ferreira and J. Tito Mendonca