Haider ع. أ. (2017) “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(2), pp. 267–277. doi: 10.47372/uajnas.2017.n2.a06.