Aspects of predicative algebraic set theory I: Exact completion.

Benno van den Berg Ieke Moerdijk Aspects of predicative algebraic set theory I: Exact completion. 123-159 2008 156 Ann. Pure Appl. Logic 1 http://dx.doi.org/10.1016/j.apal.2008.06.013 db/journals/apal/apal156.html#BergM08