A seasonal cycle and an abrupt change in the variability characteristics of the intraday variable source S4 0954+65N. Marchili, T. P. Krichbaum, X. Liu, H.-G. Song, K. É. Gabányi, L. Fuhrmann, A. Witzel and J. A. ZensusA&A, 542 (2012) A121DOI: https://doi.org/10.1051/0004-6361/201218977