1. Butterflies in a semi-abelian context;Abbad;Adv. Math.,2013
2. Faithful calculus of fractions;Abbad;Cah. Topol. Géom. Différ. Catég.,2013
3. Exact Categories;Barr,1971
4. Some remarks on 2-categorical algebra;Bénabou;Bull. Soc. Math. Belg.,1989
5. Handbook of Categorical Algebra, vol. 1;Borceux,1994