On the weak Sard property

Roman V. Dribas, Andrew S. Golovnev, Nikolay A. Gusev

If $f:[0,1{]}^2\to \mathbb{R}$ is of class $C^2$ then Sard's theorem implies that $f$ has the following relaxed Sard property: the image under $f$ of the Lebesgue measure rest…