Karshenboim, Savely G. Laser Spectroscopy, Max Planck Institute of Quantum Optics, Max Planck Society;
Puchalski, M., Czarnecki, A., & Karshenboim, S. G. (2007). Positronium-Ion Decay. Physical Review Letters, 99(20): 203401. doi:10.1103/PhysRevLett.99.203401.