The dominion of Isbell

Barry Mitchell
1972 Transactions of the American Mathematical Society  
A well-known characterization of epimorphisms in the category of rings with identity is imitated to give a similar characterization of epimorphisms in the category of small pre-additive categories. From this one deduces IsbelFs "Zigzag Theorem" concerning epimorphisms in Cat.
doi:10.1090/s0002-9947-1972-0294441-0 fatcat:gki57k2bk5f6hlltzdtlauql3y