  The well-known identity involving the expression presented in the above title
is considered in Riemannian and in Euclidean space without restriction on the
coordinate system adopted therein. The Riemann and Ricci tensors intrinsically
assume a defining role in the analysis. The analysis is designed to put an end
to the myriad of confusing and mostly incorrect statements about the identity,
which are found in textbooks and in the literature.
