Aserrar, Youssef, and Elhoucien Elqorachi. “Cosine and Sine Addition and Subtraction Law With an Automorphism”. Annales Mathematicae Silesianae 38, no. 2 (November 29, 2023): 155–176. Accessed May 6, 2025. https://trrest.vot.pl/ojsus/index.php/AMSIL/article/view/16429.