D. X. Khoa, L. V. Doai, P. V. Trong, T. M. Cuong, V. N. Sau, N. H. Bang and L. N. M. Anh, EIT enhanced self-Kerr nonlinearity in the three-level lambda system under Doppler broadening, Comm. Phys. 24 (2014) 217. DOI: https://doi.org/10.15625/0868-3166/24/3/3915.