Very high energy outburst of Markarian 501 in May 2009. - Aliu, E.; Archambault, S.; Archer, A.; Arlen, T.; Aune, T.; Barnacka, A.; Behera, B.; Beilicke, M.; Benbow, W.; Berger, K.; Bird, R.; Böttcher, M.; et al. (Astronomy & Astrophysics / Astronomie et Astrophysique, 2016)