1. Adams, R.A.: Sobolev spaces. New York, San Francisco, London: AcademicPress 1975
2. Agmon, S.: TheL p approach to the Dirichlet problem. Ann. Sc. Norm. Super. Pisa (3)13, 405?448 (1959)
3. Amick, C.J., Fraenkel, L.E.: The uniqueness of Hill's spherical vortex. Arch. Ration. Mech. Anal.92, 91?119 (1986)
4. Bandle, C.: Isoperimetric inequalities and applications. Boston, London, Melbourne: Pitman 1980
5. Lect. Notes Math.;T.B. Benjamin,1976