Two-phonon structures for beta-decay theory A.P. Severyukhin, N.N. Arsenyev, I.N. Borzov, R.G. Nazmitdinov and S. Åberg EPJ Web Conf., 194 (2018) 02008 Published online: 14 November 2018 DOI: 10.1051/epjconf/201819402008