Long-term spectroscopy of η Carinae - I. The high and low excitation phasesA. Damineli, O. Stahl, A. Kaufer, B. Wolf, G. Quast and D. F. LopesAstron. Astrophys. Suppl. Ser., 133 3 (1998) 299-316DOI: https://doi.org/10.1051/aas:1998461