1. E. Biémont, C.J. Zeippen, J. Phys. IV France 01, 209 (1991)
2. E. Biémont, C.J. Zeippen, Phys. Scr. 1996, 192 (1996)
3. D.E. Osterbrock, G.J. Ferland, Astrophysics of gaseous nebulae and active galactic nuclei 2nd ed (2006)
4. E. Pian, P. D’Avanzo, S. Benetti, M. Branchesi, E. Brocato, S. Campana, E. Cappellaro, S. Covino, V. D’Elia, J.P.U. Fynbo et al., Nature 551, 67 (2017), arXiv:1710.05858
5. S.J. Smartt, T.W. Chen, A. Jerkstrand, M. Coughlin, E. Kankare, S.A. Sim, M. Fraser, C. Inserra, K. Maguire, K.C. Chambers et al., Nature 551, 75 (2017). arXiv:1710.05841