Ballmann, Werner Max Planck Institute for Mathematics, Max Planck Society;
Polymerakis, Panagiotis Max Planck Institute for Mathematics, Max Planck Society;
https://dx.doi.org/10.1142/S0129167X21400188 (出版社版)
https://doi.org/10.48550/arXiv.2110.04712 (プレプリント)
Ballmann, W., & Polymerakis, P. (2021). Bottom of spectra and coverings of orbifolds. International Journal of Mathematics, 32(12):. doi:10.1142/S0129167X21400188.