To the Theory of Unstable States
  Deviations of the decay law from exponents are discussing for a long time, however, experimental proofs of such deviations are absent. Here in the general form is shown that the conclusions about non-exponential contributions are due to the disregarding of advanced interactions, i.e. at principally non-relativistic considerations. We consider decay processes in the frame of interactions duration of the quantum field theory. We show that at this basis the usual exponential decay has place. 
Sergei G. Matinyan and Mark E. Perel'man