A bridge between Dubovitskii - Federer theorems and the coarea formula

Piotr Hajlasz, Mikhail V. Korobkov, Jan Kristensen

The Morse-Sard theorem requires that a mapping $v:R^n\to R^m$ is of class $C^k$, $k>n-m$. In 1957 Dubovitski\uı generalized this result by proving that almost all level sets for a…