Echoes and quasi-normal modes of perturbations around Schwarzschild traversable wormholes Hao Yang, Zhong-Wu Xia and Yan-Gang Miao Eur. Phys. J. C, 85 7 (2025) 742 Published online: 05 July 2025 DOI: 10.1140/epjc/s10052-025-14446-w