Non-abelian Extensions of Lie 2-algebras
  In this paper, we introduce the notion of derivations of Lie 2-algebras and construct the associated derivation Lie 3-algebra. We prove that isomorphism classes of non-abelian extensions of Lie 2-algebras are classified by equivalence classes of morphisms from a Lie 2-algebra to a derivation Lie 3-algebra. 
Shaohan Chen, Yunhe Sheng, Zhujun Zheng
math-ph math.MP