Key points are not available for this paper at this time.
1) Manifolds, mappings, tensor fields and other geometric objects are assumed to be differentiate and of class C°°.2) In 3, a vector field X is called a concurrent vector field if there exists a function / such that dx+D(fX)=Q, but in this paper, we adopt the above definition.
Yano et al. (Fri,) studied this question.