Ershov Yu. L. 
          Elementary regular rings. II
        We extend the well-known result by Burris and Werner on existence of 
          defining sequences for elementary products of models to arbitrary enrichments 
          of Boolean algebras (we obtain a complete analog of the Feferman–Vaught 
          theorem). This enables us to establish decidability of the elementary 
          theory of a classical object of number theory, the ring of adeles.