Haider عبدالناصر أمين. “Geometrical Invariant element’s in Theory 2F- Mapping Between Riemannian Spaces A\(_n\) Which Have Tensors (F)\(^3\)=0”. University of Aden Journal of Natural and Applied Sciences 21, no. 2 (August 31, 2017): 267–277. Accessed May 18, 2024. https://uajnas.adenuniv.com/index.php/uajnas/article/view/251.