Hirosawa, Fumihiko, and Michael Reissig. “About the Optimality of Oscillations in Non-Lipschitz Coefficients for Strictly Hyperbolic Equations”. ANNALI SCUOLA NORMALE SUPERIORE - CLASSE DI SCIENZE 3, no. 3 (December 14, 2009): 589-608. Accessed May 26, 2026. https://journals-dev.sns.it/index.php/annaliscienze/article/view/49.