Properties of Hadamard directional derivatives: Denjoy-Young-Saks theorem for functions on Banach spaces

Ludek Zajicek

The classical Denjoy-Young-Saks theorem on Dini derivatives of arbitrary functions $f:\mathbb{R}\to \mathbb{R}$ was extended by U.S. Haslam-Jones (1932) and A.J. Ward (1935) to arbitrary functio…