Emission spectra and intrinsic optical bistability in a two-level medium M.G. Gladush, D.V. Kuznetsov and Vl.K. Roerich Eur. Phys. J. D, 64 2-3 (2011) 511-520 Published online: 06 October 2011 DOI: 10.1140/epjd/e2011-20194-0