Towards equation of state of dark energy from quasar monitoring: Reverberation strategy B. Czerny, K. Hryniewicz, I. Maity, A. Schwarzenberg-Czerny, P. T. Życki and M. Bilicki A&A, 556 (2013) A97 Published online: 02 August 2013 DOI: 10.1051/0004-6361/201220832