Crossed modules for Lie 2-algebras
  The notion of crossed modules for Lie 2-algebras is introduced. We show that, associated to such a crossed module, there is a strict Lie 3-algebra structure on its mapping cone complex and a strict Lie 2-algebra structure on its derivations. Finally, we classify strong crossed modules by means of the third cohomology group of Lie 2-algebras. 
Honglei Lang and Zhangju Liu
math.RA math-ph math.MP