Setiawati, S., U. A. Zahro, N. A. Robbaniyyah, and I. L. Ihwani. “Design of Facial Expressions Recognition for Academic Presence By Using Backpropagation Artificial Neural Networks Based on Principal Components Analysis”. Semeton Mathematics Journal, vol. 1, no. 2, Oct. 2024, pp. 97-104, doi:10.29303/semeton.v1i2.240.