1. E. R. Andrew, Nuclear Magnetic Resonance [Russian translation] (IL, Moscow, 1957).
2. H. Dehmelt, Am. J. Phys.22, 110 (1954).
3. I. Shpigel', M. Raizer, and É. Myaé, Zhur. Tekh. Fiz.27, 387 (1957).
4. M. Buyle-Bodin, J. Phys. Radium20, 159A (1959).
5. N. Hopkins, Rev. Sci. Instr.20, 401 (1949).