Bahar Uyar Düldül. “Extended Darboux Frame Field in Minkowski Space-Time $\mathbb{E}_1^4$”. Malaya Journal of Matematik 6, no. 03 (July 1, 2018): 473–477. Accessed April 7, 2025. https://www.malayajournal.org/index.php/mjm/article/view/823.