When different norms lead to same billiard trajectories?
A. Akopyan, R. Karasev, European Journal of Mathematics 8 (2022) 1309–1312.

Coarse infinite-dimensionality of hyperspaces of finite subsets
T. Weighill, T. Yamauchi, N. Zava, European Journal of Mathematics (2021).

Billiards in ellipses revisited
A. Akopyan, R. Schwartz, S. Tabachnikov, European Journal of Mathematics (2020).

Tropical formulae for summation over a part of SL(2,Z)
N. Kalinin, M. Shkolnikov, European Journal of Mathematics 5 (2019) 909–928.