Some symmetry problems are formulated and solved. New simple proofs are given for some symmetry problems studied earlier. One of the results is as follows: if a single-layer potential of a surface, homeomorphic to a sphere, with a constant charge density, is equal to c/|x| for all sufficiently large |x|, where c > 0 is a constant, then the surface is a sphere.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-ap96-1-5, author = {N. S. Hoang and A. G. Ramm}, title = {Symmetry problems 2}, journal = {Annales Polonici Mathematici}, volume = {95}, year = {2009}, pages = {61-64}, zbl = {1169.53320}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-ap96-1-5} }
N. S. Hoang; A. G. Ramm. Symmetry problems 2. Annales Polonici Mathematici, Tome 95 (2009) pp. 61-64. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-ap96-1-5/