HOFFMANN-JORGENSEN, J. On the Differentiability Points of a Function of Two Real Variables Admitting Partial Derivatives. MATHEMATICA SCANDINAVICA, [S. l.], v. 35, p. 259–266, 1974. DOI: 10.7146/math.scand.a-11551. Disponível em: https://www.mscand.dk/article/view/11551. Acesso em: 30 apr. 2024.