1. K. Scholle, S. Lamrini, P. Koopmann, P. Fuhrberg, in Frontiers in Guided Wave Optics and Optoelectronics (InTech, Vukovar, 2010), pp. 471–500
2. T.Y. Fan, G. Huber, R.L. Byer, IEEE J. Quantum Electron. 23, 924 (1988)
3. L. Pauling, M. Shappel, Z. Kristallogr. 75, 128 (1930)
4. A.A. Kaminskii, Laser Crystals (Springer, Berlin, 1990)
5. L. Fornasiero, Nd3+- und Tm3+-dotierte sesquioxide. Ph.D. thesis, Universität Hamburg (1999)