2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/9305We present results of modeling of spectra of M-, L-, T-dwarfs. Theoretical spectra are fitted to observed spectra to study the main parameters of the low-mass objects beyond the bottom of Main Sequence. Application of ``lithium'' and ``deuterium'' tests for assessment of ultra-cool dwarfs are discussed.Talk for MAO2004 Meeting (Kyiv, July 15-17, 2004), see more details on http://www.mao.kiev.ua/mao-2004/public.htm, 6 pages, 3figsAstrophysicstext