1. I. Solomon, Phys. Rev. 99, 559 (1955).PHRVAO0031-899X
2. N. Bloembergen, J. Chem. Phys. 27, 572 (1957); JCPSA60021-9606
3. N. Bloembergen, 27, 595 (1957).JCPSA60021-9606, J. Chem. Phys.
4. N. Bloembergen and L. O. Morgan, J. Chem. Phys. 34, 842 (1961).JCPSA60021-9606
5. A. Abragam and B. Bleaney, Electron Paramagnetic Resonance of Transition Ions (Dover, New York, 1970).