The Pierre Auger Observatory V: Enhancements
  Ongoing and planned enhancements of the Pierre Auger Observatory 
The Pierre Auger Collaboration: P. Abreu, M. Aglietta, E.J. Ahn,   I.F.M. Albuquerque, D. Allard, I. Allekotte, J. Allen, P....
astro-ph.IM astro-ph.HE hep-ex physics.ins-det