Polarization and photometric observations of the gamma-ray blazar PG 1553+113I. Andruchow, J. A. Combi, A. J. Muñoz-Arjonilla, G. E. Romero, S. A. Cellone and J. MartíA&A, 531 (2011) A38DOI: https://doi.org/10.1051/0004-6361/201016009
