1. Butterflies I: Morphisms of 2-group stacks;Aldrovandi;Adv. Math.,2009
2. Extensions of symmetric cat-groups;Bourn;Homology, Homotopy Appl.,2002
3. Bitorseurs et cohomologie non abélienne;Breen,1990
4. Théorie de Schreier supérieure;Breen;Ann. Sci. École Norm. Sup. (4),1992
5. Notes on 1- and 2-gerbes;Breen,2009