N. A. Tuan, N. V. Thanh, T. T. T. Nu, N. H. Sinh, V. V. Khai, D. H. Chi and S.- ichi Katayama, Computational Design of Mn<SUB>4</SUB> Molecules with Strong Intramolecular Exchange Coupling, Comm. Phys. 21 (2011) 137. DOI: https://doi.org/10.15625/0868-3166/21/2/108.