1. P. Schneider, J. Ehlers, and E. E. Falco, Gravitational Lenses (Springer, New York, 1992).
2. S. N. Gninenko, N. V. Krasnikov, and V. A. Matveev, Phys. Usp. 64, 1286 (2021).
3. J. Alexander et al. (The Dark Sector Collab.), arXiv: 1608.08632.
4. D. Banerjee et al. (The NA64 Collab.), CERN-SPSC2019-002/SPSC-P-359.
5. G. W. Bennett et al. (The Muon g-2 Collab.), Phys. Rev. D 73, 072003 (2006).