Spectral and luminosity classification for the cool components in symbiotic starsZ. X. Zhu, M. Friedjung, G. Zhao, H. R. Hang and C. C. HuangAstron. Astrophys. Suppl. Ser., 140 1 (1999) 69-78DOI: https://doi.org/10.1051/aas:1999117