1. See for example, R Rajaraman, Solitons and Instantons (North Holland Publishing Company, Amsterdam, 1982) and references therein
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4. W A Bardeen, S D Drell, M Weinstein and T M Yan,Phys. Rev. D11, 1094 (1975)
5. R Friedberg and T D Lee,Phys. Rev. D16, 1096 (1977);D17, 2623 (1978)