We generalize to Banach spaces the Thibault-Zagrodny Theorem that if f and g are primal lower regular functions and ∂f = ∂g locally, then f and g locally differ by a constant. Our method consists in a reduction to considerations of slopes.

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M. Ivanov, M. Konstantinov, N. Zlateva. “Subdifferential Determination of a Primal Lower Regular Function on a Banach Space.” Journal of Convex Analysis 33 (2026), No. 1&2, 497–516. https://doi.org/10.68381/jca33031