Let $R$ be a ring. According to [this MO question](https://mathoverflow.net/questions/59282/sums-compact-objects-f-g-objects-in-categories-of-modules), the modules $M \in R\text{-Mod}$ such that $\text{Hom}(M, -)$ preserves all filtered colimits (the [compact objects](http://ncatlab.org/nlab/show/compact+object)) are precisely the finitely-presented modules. Where can I find a proof of this?