Three-Loop Radiative-Recoil Corrections to Hyperfine Splitting Generated   by One-Loop Fermion Factors
  We consider three-loop radiative-recoil corrections to hyperfine splitting in muonium generated by diagrams with one-loop radiative photon insertions both in the electron and muon lines. An analytic result for these nonlogarithmic corrections of order $\alpha(Z^2\alpha)(Z\alpha)(m/M)\widetilde E_F$ is obtained. This result constitutes a next step in the implementation of the program of reduction of the theoretical uncertainty of hyperfine splitting below 10 Hz. 
Michael I. Eides (University of Kentucky, USA, and Petersburg Nuclear   Physics Institute, Russia), Howard Grotch (Universit...