X-ray photoelectron spectra and features of the electronic-energy structure of oxygen-stabilized phases of Zr4Fe2O and Zr4Ni2O - A. A. Lavrentev; P. N. Shkumat; E. I. Kopylova; B. V. Gabreljan; A. K. Sinelnichenko; Ju. Zavalij; Ju. Khizhun (Reports of the National Academy of Sciences of Ukraine, 2014)