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3. I. L. Landau and Yu. V. Sharvin,Sov. Phys.-JETP Lett. 15, 59 (1972).
4. I. L. Landau,Sov. Phys.-JETP 37, 285 (1973).
5. I. L. Landau,Sov. Phys.-JETP 40, 126 (1974).