1. D. Holcomb, R. Norberg: Phys. Rev.98, 1074 (1955)
2. For the earlier literature see, e.g.: A. Abragam:The Principles of Nuclear Magnetism (Clarendon Press, Oxford 1961)
3. I. Ebert, G. Seifert:Kernspinresonanz im Festkörper (Akademische Verlagsges., Leipzig 1966)
4. M. Goldman:Spin Temperature and Magnetic Resonance in Solids (Clarendon Press Oxford 1970)
5. J. Winter:Magnetic Resonance in Metals (Clarendon Press, Oxford 1971)