Ivanov, Milen, and Nadia Zlateva. “Hadamard Inverse Function Theorem Proved by Variational Analysis”. Serdica Mathematical Journal 49, no. 1–3 (November 20, 2023): 97–106. Accessed October 26, 2026. https://serdica.math.bas.bg/index.php/serdica/article/view/37.