1. B.P. Abbott, R. Abbott, T.D. Abbott et al., Phys. Rev. X 9, 031040 (2019)
2. R. Abbott, T.D. Abbott, S. Abraham et al., Phys. Rev. X 11, 021053 (2021)
3. M. Abdul-Masih, G. Banyard, J. Bodensteiner et al., Nature 580, E11 (2020)
4. C. Aerts, J. Puls, M. Godart, M.A. Dupret, A &A 508, 409 (2009)
5. D. Baade, A &A 135, 101 (1984)