Rapid polarization variations at 20 cm in 0917+624 S. J. Qian, A. Witzel, A. Kraus, T. P. Krichbaum and J. A. Zensus A&A, 367 3 (2001) 770-779 Published online: 15 March 2001 DOI: 10.1051/0004-6361:20000465