Yerokhin, V. A., Artemyev, A. N., Shabaev, V. M., Sysak, M. M., Zherebtsov, O. M., & Soff, G. (2000). Two-photon exchange corrections to the 2p(1/2)-2s transition energy in Li-like high-Z ions. Physical Review Letters, 85, 4699-4702.