New two-colour light curves of Q0957+561: time delays and the origin of intrinsic variationsV. N. Shalyapin, L. J. Goicoechea, E. Koptelova, A. Ullán and R. Gil-MerinoA&A, 492 2 (2008) 401-410DOI: https://doi.org/10.1051/0004-6361:200810447
