On the endomorphisms of Weyl modules over affine Kac-Moody algebras at   the critical level
  We present an independent short proof of the main result of arXiv:0706.3725 that the algebra of endomorphisms of a Weyl module of critical level is isomorphic to the algebra of functions on the space of monodromy-free opers on the disc with regular singularity and residue determined by the highest weight of the Weyl module. We derive this from the results of arXiv:0712.1183 about the shift of argument subalgebras. 
Boris Feigin, Edward Frenkel, Leonid Rybnikov