Calanchi, Marta, Carlos Tomei, and André Zaccur. “Cusps and a Converse to the Ambrosetti-Prodi Theorem ”. ANNALI SCUOLA NORMALE SUPERIORE - CLASSE DI SCIENZE 18, no. 2 (December 27, 2017): 483-507. Accessed February 20, 2026. https://journals.sns.it/index.php/annaliscienze/article/view/586.