Matching of Singly- and Doubly-Unresolved Limits of Tree-level QCD   Squared Matrix Elements
  We describe how to disentangle the singly- and doubly-unresolved (soft and/or collinear) limits of tree-level QCD squared matrix elements. Using the factorization formulae presented in this paper, we outline a viable general subtraction scheme for computing next-to-next-to-leading order corrections for electron-positron annihilation into jets. 
G\'abor Somogyi, Zolt\'an Tr\'ocs\'anyi and Vittorio Del Duca