Wayne M. Itano, James C. Bergquist, John J. Bollinger, Jonathan Mark Gilligan, Daniel J. Heinzen, Fred L. Moore, Mark G. Raizen, & David J. Wineland, Ultra-high precision spectroscopy for fundamental physics, Hyperfine Interactions 78, 211–220 (1993). Abstract:
Wayne M. Itano, James C. Bergquist, John J. Bollinger, Jonathan Mark Gilligan, Daniel J. Heinzen, Fred L. Moore, Mark G. Raizen, & David J. Wineland, Ultra-high precision spectroscopy for fundamental physics, Hyperfine Interactions 78, 211–220 (1993).