Fotsing Tetsing, Hans, Cyriaque Atindogbé, and Ferdinand Nkageu. “Normalized Null Hypersurfaces in the Lorentz-Minkowski Space Satisfying $L_r X =U X +b$”. Tamkang Journal of Mathematics 54, no. 4 (August 21, 2022): 353–378. Accessed June 14, 2024. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/4851.