1. S. Geschwind: ”Optical Techniques in EPR in Solids”, in Electron Paramagnetic Resonance, ed. by S. Geschwind (Plenum, New York 1972)
2. I.Y. Chan: ”Zero Field ODMR Techniques - Phosphorescence Detection”, in Triplet State ODMR Spectroscopy: Techniques and Applications to Biophysical Systems, ed. by R.H. Clarke (Wiley, New York 1982)
3. D.W. Pratt: ”ODMR Studies of Excited Triplet States in High Fields”, in Triplet state ODMR Spectroscopy, ed. by R.H. Clarke (Wiley, New York 1982)
4. D.B. Fichten: ”Zero Phonon Transitions”, in Physics of Color Centers, ed. by W.B. Fowler (Academic, New York 1968) Chap. 5
5. H. Henry, C.P. Slichter: ”Moments in the Degeneracy of Optical Spectra”, in Physics of Color Centers, ed. by W.B. Fowler (Academic, New York 1968) Chap. 6