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3. For recent work see: Kurkijärvi, J., Rainer, D.: Helium three. In: Modern problems in condensed matter sciences. Amsterdam: North-Holland 1990
4. Lin, S.Y., Yang, Y.: J. Comput. Phys.89, 257 (1990)
5. Zurek, W.H.: Nature13, 505 (1985)