On monoidal functors between (braided) Gr-categories
  In this paper, we state and prove precise theorems on the classification of the category of (braided) categorical groups and their (braided) monoidal functors, and some applications obtained from the basic studies on monoidal functors between categorical groups. 
Nguyen Tien Quang, Nguyen Thu Thuy, Pham Thi Cuc
math.CT