Spectral classification of O–M stars on the basis of UBV photometryV. I. Kuznetsov, G. Z. Boutenko, G. A. Lazorenko and P. F. LazorenkoAstron. Astrophys. Suppl. Ser., 142 3 (2000) 389-398DOI: https://doi.org/10.1051/aas:2000159