Abdo A.A, Ackermann M., Ajello M., Baldini L., Ballet J., Barbiellini G., Bastieri D., Bechtol K., Bellazzini R., Berenji B. et al..  2011.  Fermi Large Area Telescope Observations of Markarian 421: The Missing Piece of its Spectral Energy Distribution. The Astrophysical Journal. 736:131.

Abdo A.A, Ackermann M., Ajello M., Allafort A., Baldini L., Ballet J., Barbiellini G., Baring M.G, Bastieri D., Bechtol K. et al..  2011.  Insights into the High-energy $\gamma$-ray Emission of Markarian 501 from Extensive Multifrequency Observations in the Fermi Era}. The Astrophysical Journal. 727:129.

Acciari V.A, Arlen T., Aune T., Beilicke M., Benbow W., Böttcher M., Boltuch D., Bradbury S.M, Buckley J.H, Bugaev V. et al..  2011.  Spectral Energy Distribution of Markarian 501: Quiescent State Versus Extreme Outburst. The Astrophysical Journal. 729:2.