Central extensions and reciprocity laws on algebraic surfaces
  We consider an algebraic surface. For an irreducible curve on this surface and for a point on this curve one can associate an artinian ring, which is a sum of two-dimensional local fields. An example of two-dimensional local field is iterated Laurent series. We consider an integer value symbol on a two-dimensional local field. This symbol appears for the description of non-ramified coverings of two-dimensional local fields and for the description of intersection index of divisors on surfaces by adeles. We interpret this symbol as the commutator of lifting of elements in the central extension of the multiplicative group of two-dimensional local field. We prove the reciprocity laws around the points and along the projective curves on the surface. The proof uses the adelic ring on the surface and is similar to the Tate method for the residue of differentials on a projective curve. 
D.V. Osipov