Bibcode
                                    
                            Takalo, L. O.; Sillanpaa, A.; Nilsson, K.; Kidger, M.; de Diego, J. A.; Piirola, V.
    Bibliographical reference
                                    Astronomy and Astrophysics Supplement Series (ISSN 0365-0138), vol. 94, no. 1, July 1992, p. 37-42.
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                        7
            
                        1992
            
  Citations
                                    68
                            Refereed citations
                                    65
                            Description
                                    Results are presented from simultaneous UBVRI photopolarimetric
observations of eight blazars at the 2.56-m Nordic Optical Telescope
during winter 1991. In 3C 66A the highest ever measured polarization,
P(U) = 30.5 percent is observed, with small frequency dependence (FDP),
P being lower toward longer wavelengths. In AO 0235 + 164, large changes
in the polarization level and in the FDP between different nights were
detected. The FDP is seen to be three times more common than the
frequency dependence in the position angle in these blazars.