Mrk 421

[References]

Whipple: Punch, M. et al., Nature 358,477 (1992)
           Schubnell, M.S. et al., ApJ 460, 644 (1996)
           Zweerink, J.A. et al., ApJ 490, L141 (1997)
           Krennrich, F. et al., ApJ 511, 149-156 (1999)
           Krennrich, F. et al., ApJ 575, L9-L13 (2002)
           Blazejowski, M. et al., ApJ 630, 130-141 (2005)
           Konopelko, A. et al., Proc. 30th ICRC (2007) / arXiv:0708.3857 [astro-ph]
           Daniel, M.K. et al., Gamma 2008 /arXiv:0810.0387
           Horan, D. et al., arXiv:0901.1225

HEGRA: Petry, D. et al., A&A 311,  L13-L16 (1996)
            Aharonian, F.A. et al., A&A 350, 757-764 (1999)
            Aharonian, F. et al., ApJ 546, 8980902 (2001)
            Aharonian, F. et al., A&A 393, 89-99 (2002)

Whipple and HEGRA: Fosatti, G. et al., ApJ 677, 906-925 (2008)

CAT: Piron, F. et al., A&A 374, 895-906 (2001)

CANGAROO-II: Okumura, K. et al., ApJ 579, L9-L12 (2002)

STACEE: Boone, L.M. et al., ApJ 579, L5-L8 (2002)

Tibet AS-gamma: Amenomori, M. et al., ApJ 598, 242-249 (2003)

Milagro: Atkins, R. et al., Astrophys. J. 608, 680 (2004)

H.E.S.S.: Aharonian, F. et al., Astron.Astrophys. 95 (2005) 437

MAGIC: Albert, J. et al., ApJ 663, 125-138 (2007)
           F.Goebel et al., 30th ICRC (2007) / arXiv:0709.2032 [astro-ph]

VERITAS: S.J. Fegan et al., 30th ICRC (2007) / arXiv:0709.3659 [astro-ph]

Agile, Gasp-Webt, MAGIC, VERITAS : I. Donnaurumma et al., arXiv:0812.1500 [astro-ph]