Extension of the Cosmic Ray Energy Spectrum Beyond the Predicted Greisen-Zatsepin-Kuz'min Cutoff
Takeda, M. et al.1998, Phys. Rev., 81,1163.

Study of Broad Scale Anisotropy of Cosmic Ray Arrival Directions from 2 X 10¹⁷eV to 10²⁰eV from Fly's Eye Data
D.J.Bird et al.1998, Jun. 6.

The Highest Energy Cosmic Rays
O'Halloran, T. et al.1998, Phys. Today, Jan,31.