Phase diagram of the alternating-spin Heisenberg chain with extra isotropic three-body exchange interactionsNedko B. Ivanov, Jörg Ummethum and Jürgen SchnackEur. Phys. J. B, 87 10 (2014) 226DOI: https://doi.org/10.1140/epjb/e2014-50423-7