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Published online by Cambridge University Press: 19 July 2016
After a minimum in the spring of 1984, when the broad permitted lines were found to become much weaker, the spectrum of NGC 4151 became much more like a Sy 2 (Lyutyi et al., 1984; Chuvaev and Oknyanskij, 1989; Penston and Perez, 1984). Recently, this object returned to the high state after about 8 yr in the semiquiescent phase (Oknyanskij et al., 1991).