Iterated residues and multiple Bernoulli polynomials Spécialisation des éléments de \(Br_ 2({\mathbb{Q}}(T_ 1,\cdot \cdot \cdot,T_ n))\). (Specialization of elements of \(Br_ 2({\mathbb{Q}}(T_ 1,\cdot \cdot \cdot,T_ n)))\) 