Castillon, Philippe, and Berardo Ruffini. “A Spectral Characterization of Geodesic Balls in Non-Compact Rank One Symmetric Spaces”. ANNALI SCUOLA NORMALE SUPERIORE - CLASSE DI SCIENZE 19, no. 4 (December 13, 2019): 1359-1388. Accessed February 20, 2026. https://journals.sns.it/index.php/annaliscienze/article/view/666.