To the question of smoothness of isometries
As was pointed out by Yu. G. Reshetnyak the result by Calabi and Hartman that the isometric correspondence between \(C^{k,\alpha}\) manifolds belongs to the class \(C^{k+1,\alpha}\) contained some flaw. The article under review fills this gap in the last unproven cases when \((k,\alpha) = (0,1)\) and \((k,\alpha) = (1,0)\).
scientific article; zbMATH DE number 652185