New catalytic system for preparation of methyl 2 - (3 - hydroxy - 2 - oxo -2,3 - dinydro - 1H - 3 - indolyl) acrylates / V.Sargorovschi, N.Sucman [et al.] // Chemistry Journal of Moldova. General, Industrial and Ecological Chemistry. - 2010. - №5. - P.109 - 117.