1. C.S.M. Doake, P.W.F. Gribbon, Phys. Lett. 30A, 251 (1969)
2. G.G. Ihas, T.M. Sanders, Phys. Rev. Lett. 27, 383 (1971)
3. G.G. Ihas, T.M. Sanders, in Proceedings of the 13th International Conference on Low Temperature Physics, vol. 1, ed. by K.D. Timmerhaus, W.J. O’Sullivan, E.F. Hammel (Plenum, New York, 1972), p. 477
4. V.L. Eden, P.V.E. McClintock, Phys. Lett. 102A, 197 (1984)
5. V.L. Eden, P.V.E. McClintock, in 75th Jubilee Conference on Liquid 4Helium. ed. by J.G.M. Armitage (World Scientific, Singapore, 1983), p. 194