This result states bochner formula for harmonic maps: given (M,g) and (N,h) be smooth Riemannian manifolds, with M=m, and let u : M N be a smooth harmonic map. Let M and N denote the Levi-Civita connections of g and h, and let denote.... It is useful in harmonic map theory and elliptic regularity, where variational identities, curvature estimates, and compactness arguments control geometric objects.