Optical absorption spectra of finite systems from a conserving Bethe-Salpeter equation approachG. Pal, Y. Pavlyukh, W. Hübner and H. C. SchneiderEur. Phys. J. B, 79 3 (2011) 327-334DOI: https://doi.org/10.1140/epjb/e2010-10033-1