Hi all,

I was reading a proof that the localization of categories preserves abelianess. Although the author didn't mentioned explicitly, it seems to me that the proof is reduced to the statement that

An additive category is a balanced category(i.e., every monic epimorphism is an isomorphism).

I know that an abelian category is balanced, but I'm afraid not so an additive category. Any suggestions or reference?

Thanks.