New theoretical approaches for correlated systems in nonequilibriumM. Eckstein, A. Hackl, S. Kehrein, M. Kollar, M. Moeckel, P. Werner and F.A. WolfEur. Phys. J. Special Topics, 180 (2009) 217-235DOI: https://doi.org/10.1140/epjst/e2010-01219-x