K. Murase, T. Thompson, B. Lacki, and J. Beacom. (2010)cite arxiv:1012.2834Comment: 7 pages, 2 figures, accepted for publication in PRD, with extended descriptions. Conclusions unchanged.
T. Venters, M. Reno, and J. Krizmanic. (2022)cite arxiv:2206.02730Comment: 10 pages, 7 figures, 2 tables, Proceedings of the 37th International Cosmic Ray Conference (ICRC 2021).
J. Valle. (2006)cite arxiv:hep-ph/0608101Comment: Review based on lectures at the Corfu Summer Institute on Elementary Particle Physics in September 2005. To be published in the Proceedings.