A. A. Abdo, B. Allen, and T. Aune, ApJ, vol.688, p.1078, 2008.

A. Abramowski, F. Aharonian, and F. Ait-benkhali, Phys. Rev. D, vol.90, p.122007, 2014.

F. Acero, M. Ackermann, and M. Ajello, ApJS, vol.218, p.23, 2015.

F. Acero, M. Ackermann, and M. Ajello, ApJS, vol.223, p.26, 2016.

M. Ackermann, M. Ajello, and A. Albert, ApJ, vol.799, p.86, 2015.

M. Ackermann, M. Ajello, and L. Baldini, Phys. Rev. Lett, vol.121, p.241101, 2018.

M. Actis, G. Agnetta, and F. Aharonian, Exp. Astron, vol.32, p.193, 2011.

O. Adriani, G. C. Barbarino, and G. A. Bazilevskaya, Science, vol.332, p.69, 2011.

M. Aguilar, D. Aisa, and B. Alpat, Phys. Rev. Lett, vol.114, p.171103, 2015.

K. J. Andersen, M. Kachelriess, and D. Semikoz, ApJ, vol.861, p.19, 2018.

W. D. Apel, J. C. Arteaga-velázquez, and K. Bekk, ApJ, vol.848, p.1, 2017.

W. B. Atwood, A. A. Abdo, and M. Ackermann, ApJ, vol.697, p.1071, 2009.

B. Bartoli, P. Bernardini, and X. J. Bi, ApJ, vol.806, p.20, 2015.

M. Bouyahiaoui, M. Kachelriess, and D. V. Semikoz, JCAP, p.46, 1901.

P. Bruel, T. H. Burnett, and S. W. Digel, , 2018.

M. Cataldo, G. Pagliaroli, V. Vecchiotti, and F. L. Villante, J. Cosmol. Astropart. Phys, vol.12, p.50, 2019.

D. D. Dzhappuev, I. M. Dzaparova, and E. A. Gorbacheva, EPJ Web Conf, vol.207, p.3004, 2019.

A. Esmaili and P. D. Serpico, JCAP, vol.11, p.54, 2013.

P. C. Frisch, S. Redfield, and J. D. Slavin, ARA&A, vol.49, p.237, 2011.

D. Gaggero, A. Urbano, M. Valli, and P. Ullio, Phys. Rev. D, vol.91, p.83012, 2015.

G. Giacinti, M. Kachelriess, and D. V. Semikoz, JCAP, vol.1807, p.51, 2018.

N. Gorbunov, V. Grebenyuk, and D. Karmanov, , 2018.

M. Kachelrieß, A. Neronov, and D. V. Semikoz, Phys. Rev. Lett, vol.115, p.181103, 2015.

M. Kachelrieß, A. Neronov, and D. V. Semikoz, Phys. Rev. D, vol.97, p.63011, 2018.

M. Kachelrieß, O. E. Kalashev, M. Kuznetsov, and . Yu, Phys. Rev. D, vol.98, p.83016, 2018.

M. Kachelrieß and D. V. Semikoz, Prog. Part. Nucl. Phys, vol.109, p.103710, 2019.

P. Lipari and S. Vernetto, Phys. Rev. D, vol.98, p.43003, 2018.

K. Murase, R. Laha, S. Ando, and M. Ahlers, Phys. Rev. Lett, vol.115, p.71301, 2015.

A. Neronov and D. V. Semikoz, ApJ, vol.757, p.61, 2012.

A. Neronov and D. V. Semikoz, Phys. Rev. D, vol.85, p.83008, 2012.

A. Neronov, D. Semikoz, and C. Tchernin, Phys. Rev. D, vol.89, p.103002, 2014.

A. Neronov, D. Malyshev, A. Neronov, and D. Semikoz, Astropart. Phys, vol.72, p.32, 2015.

A. Neronov and D. Semikoz, Astropart. Phys, vol.75, p.60, 2016.

A. Neronov, D. V. Semikoz, I. Vovk, and R. Mirzoyan, Phys. Rev. D, vol.94, p.123018, 2016.

A. Neronov, M. Kachelrieß, and D. V. Semikoz, Phys. Rev. D, vol.98, p.23004, 2018.

A. M. Taylor, S. Gabici, and F. Aharonian, Phys. Rev. D, vol.89, p.103003, 2014.

R. Yang, F. Aharonian, and C. Evoli, Phys. Rev. D, vol.93, p.123007, 2016.

Y. S. Yoon, T. Anderson, and A. Barrau, ApJ, vol.839, p.5, 2017.

S. N. Zhang, O. Adriani, and S. Albergo, Ultraviolet to Gamma Ray, Space Telescopes and Instrumentation, vol.9144, p.91440, 2014.