Collective treatment of the isovector pair correlations: Boson representation G. Nikoghosyan, E. A. Kolganova, D. A. Sazonov and R. V. Jolos Eur. Phys. J. A, 55 10 (2019) 189 Published online: 30 October 2019 DOI: 10.1140/epja/i2019-12897-8