The Problem of Search and Observation of Gamma-Quanta Sources with Energies 1012 - 1013 eV Akopyan, A. M. ; Matyazov, S. H. ; Nikolsky, S. I. ; Sinitsina, N. G. Abstract Publication: International Cosmic Ray Conference Pub Date: August 1991 Bibcode: 1991ICRC....2..653A