The main idea of this paper is to introduce the notion of a Schreier 2-category and of a crossed semimodule over categories and to prove the categorical equivalence between their categories.
"Crossed semimodules of categories and Schreier 2-categories." Tbilisi Math. J. 11 (2) 47 - 57, June 2018. https://doi.org/10.32513/tbilisi/1529460021