Observations of Mkn 421 during 1997 and 1998 in the energy range above 500 GeV with the HEGRA stereoscopic Cherenkov telescope system - Aharonian, Felix A.; Akhperjanian, A. G.; Andronache, M.; Barrio, J. A.; Bernlöhr, Konrad; Bojahr, H.; Calle, I.; Contreras, J. L.; Cortina, J.; Daum, A.; Deckers, T.; Denninghoff, S.; et al. (Astronomy and astrophysics, 1999)
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