Multi-periodicity of the Be star η Centauri from spectroscopic and photometric observationsE. Janot-Pacheco, S. Jankov, N. V. Leister, A. M. Hubert and M. FloquetAstron. Astrophys. Suppl. Ser., 137 3 (1999) 407-418DOI: https://doi.org/10.1051/aas:1999256