S. P. Knurenko, I. S. Petrov, “Estimate of the integral photon flux in the region of extremely high energies in complex Yakutsk EAS array data”, Pis'ma v Zh. Èksper. Teoret. Fiz., 107:11 (2018), 709–716; JETP Letters, 107:11 (2018), 676–683
S. P. Knurenko, I. S. Petrov, “Radio signals from extensive air showers with the energies $E_0\geq10^{19}$ eV according to data from the Yakutsk extensive air shower array”, Pis'ma v Zh. Èksper. Teoret. Fiz., 104:5 (2016), 306–310; JETP Letters, 104:5 (2016), 297–301