Some properties on Schur multiplier and cover of a pair of Lie algebras
  Similar to works of G. Ellis (1998), the concept of covering pair of Lie algebras is defined. Also, we show the existence of covering pair for the pair of Lie algebras (L,N) and then show that every crossed module is a homomorphic image of a covering pair of (L,N). Finally, under some condition, we present some inequalities for the Schur multiplier of a pair of finite dimensional Lie algebras. 
Hamid Mohammadzadeh, Behrouz Edalatzadeh
math.RA