Bell E.W., X. Guo, J.L. Forand, K. Rinn, D.R. Swenson, J.K. Thompson, G.H. Dunn, M.E. Bannister, D. Gregory, R.A. Phaneuf, and A. Smith, Physical Review A 49, 4585-4596 (1994).
Forand J.L., C. Timmer, E.K. Wåhlin, B.D. DePaola, G.H. Dunn, D.R. Swenson, and K. Rinn, Review Of Scientific Instruments 61, 3372 (1990).
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