Precision study of positronium and precision tests of the bound state   QED
  Despite its very short lifetime positronium provides us with a number of accurate tests of the bound state QED. In this note a brief overview of QED theory and precision experiments on the spectrum and annihilation decay of the positronium atom is presented. Special attention is paid to the accuracy of theoretical predictions. 
Savely G. Karshenboim (D. I. Mendeleev Institute for Metrology, St.   Petersburg and Max-Planck-Institut fuer Quantenoptik, ...