Riemannian Manifold has Zero Gaussian Curvature iff Euclidean/Historical Note

Historical Note on Riemannian Manifold has Zero Gaussian Curvature iff Euclidean
demonstrated that a Riemannian Manifold has Zero Gaussian Curvature iff Euclidean in a posthumous paper on heat conduction.

Thus the Riemann-Christoffel tensor measures how much a Riemannian manifold deviates from a Euclidean space.