H1426+428

[References]

Whipple: D. Horan et al., Astrophys. J. 571, 753 (2002); astro-ph/0202185 [correction]
            D. Petry et al., Astrophys.J. 580, 104-109 (2002)
            D. Horan et al., Proc. 28th ICRC (Tsukuba), p.2647 (2003)

HEGRA: F. Aharonian et al., Astron. Astrophys. 384, L23 (2002)
            F. Aharonian et al., Astron. Astrophys. 403, 523 (2003)

CAT: A. Djannati-Atai et al., Astron. Astrophys. 391, L25-L28 (2002)

TACTIC: S. Thoudam,  et al., Proc. 29th ICRC (Pune), Vol.4 p.363 (2005) [Upper limit]
            Yadav, K.K. et al., arXiv:0905.3994 [Upper limit] <to appear in J. Phys. G.>

STACEE: Smith, D.A. et al., Astron. Astrophys. 459, 453-464 (2006) [Upper limit]

MAGIC: V.A. Acciari et al., arXiv:1911.06680 [astro-ph]