A simultaneous 3.5 and 1.3 mm polarimetric survey of active galactic nuclei in the northern sky I. Agudo, C. Thum, J. L. Gómez and H. Wiesemeyer A&A, 566 (2014) A59 Published online: 12 June 2014 DOI: 10.1051/0004-6361/201423366