Norms of certain functions of a distinguished Laplacian on the ax + b groups
R. Akylzhanov, Y. Kuznetsova, M. Ruzhansky, H. Zhang, Mathematische Zeitschrift 302 (2022) 2327–2352.

Arithmetic of higher-dimensional orbifolds and a mixed Waring problem
T.D. Browning, S. Yamagishi, Mathematische Zeitschrift 299 (2021) 1071–1101.