Nguyen, C. C., G. S. Tran, T. P. Nghiem, J.-C. Burie, and C. M. Luong. “Real-Time Smile Detection Using Deep Learning”. Journal of Computer Science and Cybernetics, vol. 35, no. 2, June 2019, p. 135-4, doi:10.15625/1813-9663/35/2/13315.