Comment on "Two-photon approximation in the theory of electron   recombination in hydrogen" (D. Solovyev and L. Labzowsky, Phys. Rev. A 81,   062509 (2010))
  The results for the total multi-photon decay rates of the 3p and 4s levels of hydrogen, presented by D. Solovyev and L. Labzowsky within the cascade approximation, are revisited. The corrected results for certain decay channels differ from original ones of those authors sometimes by order of magnitude. Some aspects with respect to the cosmological recombination process are clarified. 
S. G. Karshenboim (Pulkovo Observatory and Max-Planck-Institut fuer   Quantenoptik), V. G. Ivanov (Pulkovo Observatory), and...
physics.atom-ph astro-ph.CO