Upper limit on the cosmic-ray photon fraction at EeV energies from the Pierre Auger Observatory
K Aamodt Gabriel Oliveira Valeriano de Barros; Airton Deppman; Marcel Araujo Silva Figueredo; Alberto Lozéa Feijó Soares; Marcelo Gameiro Munhoz; Alexandre Alarcon do Passo Suaide; Alejandro Szanto de Toledo