1. Leggett, A. J. (1987), in J. Souletie, J. Vannimenus, and R. Store (eds), Chance and Matter, North-Holland, contains a review of MQT and MQC.
2. Chudnovsky, E. M. and Gunther, L. (1988), Phys. Rev. Lett. 60, 661.
3. Barbara, B. and Chudnovsky, E. M. (1990), Phys. Lett. A 145, 205
4. Krive, I. V. and Zaslavskii, O. B. (1990), J. Phys.: Condens. Matter 2, 9457.
5. See the contributions by Simanjuntak (phonons), Stamp, Caldeira, and Loss (magnons), and Fukuyama (Stoner excitations), and references given by these authors to the original literature.