Answer on the comment by S. G. Karshenboim, V. G. Ivanov and J. Chluba
  We studied carefully the comment by S. G. Karshenboim, V. G. Ivanov and J. Chluba to our paper "Two-photon approximation in the theory of the electron recombination in hydrogen" and found this comment erroneous. 
L. Labzowsky and D. Solovyev
physics.atom-ph