Julia Kelly and Linda Eells have published "Global Scholarship: The Role of Subject Repositories in Advancing Research from the Developing World" in College & Research Libraries News.
Here's an excerpt:
While subject repositories successfully fill a scholarly communication niche in particular disciplines, they have not been recognized for the important role they play in promoting global scholarship. Repositories such as AgEcon Search make valuable and unique contributions by increasing publishing options for researchers and thus exposing and distributing research produced in the developing world.