Green's second identity for vector fields
Summary: The second derivative of two vector functions is related to the divergence of the vector functions with first order operators. Namely, \textbf{P} \(\cdot \nabla^2\) \textbf{Q} - \textbf{Q} \(\cdot \nabla^2\) \textbf{P} \(= \nabla \cdot [\)\textbf{P}\((\nabla \cdot\) \textbf{Q}) - \textbf{Q}\((\nabla \cdot\) \textbf{P}) + \textbf{P} \(\times \nabla \times\) \textbf{Q} - \textbf{Q} \(\times \nabla \times\) \textbf{P}].
scientific article; zbMATH DE number 6092174