T. H. Nguyen, T. A. H. Nguyen, T. N. Dinh, X. K. Bui, S. T. Bui, X. C. Nguyen, V. N. Nguyen, B. T. Nguyen and D. L. Vu, Multiband Metamaterial Absorber in a Ring Structure Base on High-order Magnetic Resonance, Comm. Phys. 31 (2021) 199. DOI: https://doi.org/10.15625/0868-3166/15520.