Group gradings on finitary simple Lie algebras
  We classify, up to isomorphism, all gradings by an arbitrary abelian group on simple finitary Lie algebras of linear transformations (special linear, orthogonal and symplectic) on infinite-dimensional vector spaces over an algebraically closed field of characteristic different from 2. 
Yuri Bahturin, Matej Bre\v{s}ar, Mikhail Kochetov
math.RA