On the Order of the Schur Multiplier of a Pair of Finite p-Groups
  In 1998, G. Ellis defined the Schur multiplier of a pair $(G,N)$ of groups and mentioned that this notion is a useful tool for studying pairs of groups. In this paper, we characterize the structure of a pair of finite $p$-groups $(G,N)$ in terms of the order of the Schur multiplier of $(G,N)$ under some conditions. 
Azam Hokmabadi, Fahimeh Mohammadzadeh, Behrooz Mashayekhy
math.GR